The conventional analytical method of predicting strain in a thin film under bending is restricted to the uniform material assumption, while in flexible electronics, the film/substrate structure is widely used with mi...The conventional analytical method of predicting strain in a thin film under bending is restricted to the uniform material assumption, while in flexible electronics, the film/substrate structure is widely used with mismatched material properties taken into account. In this paper,a piecewise model is proposed to analyze the axial strain in a thin film of flexible electronics with the shear modification factor and principle of virtual work. The excellent agreement between analytical prediction and finite element results indicates that the model is capable of predicting the strain of the film/substrate structure in flexible electronics, whose mechanical stability and electrical performance is dependent on the strain state in the thin film.展开更多
In an indentation test,the effective Young's modulus of a film/substrate bilayer heterostructure varies with the indentation depth,a phenomenon known as the substrate effect.In previous studies investigating this,...In an indentation test,the effective Young's modulus of a film/substrate bilayer heterostructure varies with the indentation depth,a phenomenon known as the substrate effect.In previous studies investigating this,only the Young's modulus of the film was unknown.Once the effective Young's modulus of a film/substrate structure is determined at a given contact depth,the Young's modulus of the film can be uniquely determined,i.e.,there is a one-to-one relation between the Young's modulus of the film and the film/substrate effective Young's modulus.However,at times it is extremely challenging or even impossible to measure the film thickness.Furthermore,the precise definition of the layer/film thickness for a two-dimensional material can be problematic.In the current study,therefore,the thickness of the film and its Young's modulus are treated as two unknowns that must be determined.Unlike the case with one unknown,there are infinite combinations of film thickness and Young's modulus which can yield the same effective Young's modulus for the film/substrate.An inverse problem is formulated and solved to extract the Young's modulus and thickness of the film from the indentation depth-load curve.The accuracy and robustness of the inverse problem-solving method are also demonstrated.展开更多
Perfect Archimedes spiral cracks at micrometer scales are found in a colloid film of several hundred nanometers in thickness coated on a glass substrate.To explain the formation of this kind of spiral crack,the relati...Perfect Archimedes spiral cracks at micrometer scales are found in a colloid film of several hundred nanometers in thickness coated on a glass substrate.To explain the formation of this kind of spiral crack,the relation between the geometrical properties of the Archimedes spiral and the growth kinematics of the spiral cracks are analyzed.Meanwhile,the initiation and propagation of the spiral cracks are speculated upon logically from the specific material system based on sufficient evidence.In addition,we introduce a new cracking phenomenon and provide an insight into the new mechanism for crack propagation in soft material nano films coated on stiff substrates.展开更多
Transient thermal grating method is used to measure the thermal diffusivity of absorbing films deposited on transparent substrates. According to periodically modulated dielectric constant variations and thermoelastic ...Transient thermal grating method is used to measure the thermal diffusivity of absorbing films deposited on transparent substrates. According to periodically modulated dielectric constant variations and thermoelastic deformations of the thin films caused by the transient thermal gratings, an improved optical diffraction theory is presented. In the experiment, the probing laser beam reflectively diffracted by the thermal grating is measured by a photomultiplier at different grating fringe spaces. The thermal diffusivity of the film can be evaluated by fitting the theoretical calculations of diffraction signals to the experimental measured data. The validity of the method is tested by measuring the thermal diffusivities of absorbing ZnO films deposited on glass substrates.展开更多
We study the axisymmetric frictionless indentation problem of a piezoelectric semiconductor(PSC)thin film perfectly bonded to a semi-infinite isotropic elastic substrate by a rigid and insulating spherical indenter.Th...We study the axisymmetric frictionless indentation problem of a piezoelectric semiconductor(PSC)thin film perfectly bonded to a semi-infinite isotropic elastic substrate by a rigid and insulating spherical indenter.The Hankel integral transformation is first employed to derive the general solutions for the governing differential equations of the PSC film and elastic substrate.Then,using the boundary and interface conditions,the complicated indentation problem is reduced to numerically solve a Fredholm integral equation of the second kind.Numerical results are given to demonstrate the effects of semiconducting property,film thickness as well as Young’s modulus and Poisson’s ratio of the substrate on the indentation responses.The obtained findings will contribute to the establishment of indentation experiments for PSC film/substrate systems.展开更多
Electronics over flexible substrates offer advantages of flexibility, portability and low cost, and promising applications in the areas of energy, information, defense science and medical service. In recent years, tre...Electronics over flexible substrates offer advantages of flexibility, portability and low cost, and promising applications in the areas of energy, information, defense science and medical service. In recent years, tremendous progress has been witnessed in the development of flexible wearable devices that can be potentially massively deployed. Of particular interest are intelligent wearable devices, such as sensors and storage cells, which can be integrated by flexible magnetoelectronic devices based on magnetic thin films. To examine this further, the magnetic properties of FeNi thin films with different thicknesses grown on flexible graphene substrate are investigated at room temperature. The coercivity increases with increasing thicknesses of FeNi thin film, which can be attributed to the increase of grain size and decrease of surface roughness. Moreover, the thickness modulated magnetic property shows a magnetic anisotropy shift increase with varying thicknesses of FeNi thin film by using measurements based on ferromagnetic resonance, which further enhances the resonance frequency. In addition, the resonance peak is quite stable after bending it for ten cycles. The result is promising for the future design of flexible magnetoelectronic devices.展开更多
Doped HfO_(2)as an emerging ferroelectric material,holds considerable promise for non-volatile memory applications.Epitaxial growth of doped HfO_(2)thin films is widely adopted as an effective technique for revealing ...Doped HfO_(2)as an emerging ferroelectric material,holds considerable promise for non-volatile memory applications.Epitaxial growth of doped HfO_(2)thin films is widely adopted as an effective technique for revealing the intrinsic ferroelectric properties.In this study,based on systematic structural,chemical and electrical investigations,the influences of Mn doping and substrate orientation on ferroelectric properties of Mn-doped HfO_(2)epitaxial thin films are investigated.The results demonstrate that Mn-doped HfO_(2)thin films with orthorhombic phase can be epitaxially grown along[111]out-of-plane direction on both SrTiO_(3)(001)and(110)substrates,and 10%Mn-doping significantly stabilizes the orthorhombic polar phase and enhances the ferroelectric polarization.Interestingly,compared to the films on SrTiO_(3)(001)substrate,the better crystallinity and reduction of oxygen vacancy amount in Mn-doped HfO_(2)films grown on the SrTiO_(3)(110)substrate are observed,which enhance the remanent polarization and reduce the coercive field.It provides an effective approach for the controllable regulation of defects and the enhancement of intrinsic ferroelectricity in HfO_(2)-based materials.展开更多
Organisms have evolved a strain limiting mechanism,reflected as a non-linear elastic constitutive,to prevent large deformations from threatening soft tissue integrity.Compared with linear elastic substrates,the wrinkl...Organisms have evolved a strain limiting mechanism,reflected as a non-linear elastic constitutive,to prevent large deformations from threatening soft tissue integrity.Compared with linear elastic substrates,the wrinkle of films on non-linear elastic substrates has received less attention.In this article,a unique wrinkle evolution of the film-substrate system with a J-shaped non-linear stress-strain relation is reported.The result shows that a concave hexagonal array pattern is formed with the shrinkage strain of the film-substrate systems developing.As the interconnection of hexagonal arrays,a unit cell ridge network appears with properties such as chirality and helix.The subparagraph maze pattern formed with high compression is mainly composed of special single-cell ridge networks such as spiral single cores,chiral double cores,and combined multi-cores.This evolutionary model is highly consistent with the results of experiments,and it also predicts wrinkle morphology that has not yet been reported.These findings can serve as a novel explanation for the surface wrinkle of biological soft tissue,as well as provide references for the preparation of artificial biomaterials and programmable soft matter.展开更多
The Casimir pressure plays an important role in the adhesion stability of nanofilms at submicro scales.In this work,the Casimir pressure of peptide films deposited on a layered substrate is investigated.Three types of...The Casimir pressure plays an important role in the adhesion stability of nanofilms at submicro scales.In this work,the Casimir pressure of peptide films deposited on a layered substrate is investigated.Three types of semi-infinite substrates,i.e.,silica,silicon and gold,are considered.The buffer layer between the peptide film and substrate consists of silicon or silica.The switching sign of the Casimir pressure can be controlled in a region ranging from about 130 nm to 1000 nm,depending on the thickness of the buffer layer and the substrate.The results suggest that the critical thickness of peptide films for Casimir equilibrium increases(or decreases)by increasing the thickness of the silicon(or silica)buffer film.The influences of wetting and electrolyte screening on the Casimir pressure are also investigated.Our finding provides a theoretical guide for the adhesion stability of peptide films in organic electronics.展开更多
Thin-film nanocomposite(TFN) membranes have garnered considerable attention for their potential to improve separation performance by incorporating nanomaterials. However, challenges such as these materials' uneven...Thin-film nanocomposite(TFN) membranes have garnered considerable attention for their potential to improve separation performance by incorporating nanomaterials. However, challenges such as these materials' uneven distribution and aggregation have hindered practical applications. While prior studies have largely concentrated on modifying nanosheets for compatibility with polymer matrices, the role of substrate pore size in influencing nanosheet distribution has been overlooked. In this work, MoS_(2) nanosheets were dispersed in an aqueous phase to fabricate TFN membranes, investigating the effect of substrate pore size relative to the nanosheets. By systematically varying the particle size of MoS_(2) and the pore size of the substrate, we reveal how these factors impact material distribution and structural uniformity within the membranes. Our findings reveal that larger substrate pores allow the MoS_(2)-containing monomer solution to infiltrate more effectively, minimizing nanosheet aggregation. This enhances membrane performance by promoting better dispersion. Our results underscore the importance of considering the relative size of substrate pores and nanosheets in TFN membrane design, providing a pathway to improved material integration and higher membrane efficiency.展开更多
Amorphous Ga_(2)O_(3)(a-Ga_(2)O_(3))thin films were prepared on flexible polyimide,rigid quartz glass,and Si substrates via radio frequency magnetron sputtering at room temperature.The effect of oxygen/Ar flow rate ra...Amorphous Ga_(2)O_(3)(a-Ga_(2)O_(3))thin films were prepared on flexible polyimide,rigid quartz glass,and Si substrates via radio frequency magnetron sputtering at room temperature.The effect of oxygen/Ar flow rate ratio on the structure,optical property,surface morphology,and chemical bonding properties of the a-Ga_(2)O_(3) films was investigated.Results show that the average optical transmittance of the a-Ga_(2)O_(3) films is over 80%within the wavelength range of 300-2000 nm.The extracted optical band gap of the a-Ga_(2)O_(3) films is increased from 4.97 eV to 5.13 eV with the increase in O_(2)/Ar flow rate ratio from 0 to 0.25,due to the decrease in concentration of oxygen vacancy defects in the film.Furthermore,the optical refractive index and surface roughness of the a-Ga_(2)O_(3) films are optimized when the O_(2)/Ar flow rate ratio reaches 0.25.X-ray photoelectron spectroscopy analysis also shows that the proportion of oxygen vacancies(VO)and Ga-O chemical bonds in the O 1s peak is gradually decreased with the increase in O_(2)/Ar flow rate ratio from 0 to 0.25,proving that increasing the O_(2)/Ar flow rate ratio during film growth can reduce the concentration of oxygen vacancy defects in a-Ga_(2)O_(3) films.In this case,a-Ga_(2)O_(3) with optimal properties can be obtained.This work provides a research basis for high-performance flexible and rigid deep ultraviolet solar-blind detection devices based on a-Ga_(2)O_(3) films.展开更多
Organosilicone thin films were prepared through plasma polymerization(pp)in a plasma enhance chemical vapour deposition(PECVD)system,utilizing hexamethyldisilazane(HMDSN)as a monomer precursor,at varying distances(25 ...Organosilicone thin films were prepared through plasma polymerization(pp)in a plasma enhance chemical vapour deposition(PECVD)system,utilizing hexamethyldisilazane(HMDSN)as a monomer precursor,at varying distances(25 mm,35 mm,45 mm,55 mm,and 65 mm)from the plasma source to the substrate.Research has examined how the distance between the substrate and plasma source impacts the properties of thin films,including their thickness,surface morphology,and photoluminescence(PL).It was discovered that as the distance increased,both film thickness and PL intensity also increased.Additionally,the film was observed to be more uniform and smoother when deposited 45 mm below the plasma source.展开更多
Optimizing the orientation of β-Ga_(2)O_(3) has emerged as an effective strategy to design high-performance β-Ga_(2)O_(3) device,but the orientation growth mechanism and approach have not been revealed yet.Herein,by...Optimizing the orientation of β-Ga_(2)O_(3) has emerged as an effective strategy to design high-performance β-Ga_(2)O_(3) device,but the orientation growth mechanism and approach have not been revealed yet.Herein,by employing AlN buffer layer,the highly preferred orientation of β-Ga_(2)O_(3)(100)film rather than(-201)film is realized on 4H-SiC substrate at low sputtering power and temperature.Because β-Ga_(2)O_(3)(100)film exhibits a slower growth speed than(-201)film,the former possesses the higher dangling bond density and the lower nucleation energy,and a large conversion barrier exists between these two ori-entations.Moreover,the AlN buffer layer can suppress the surface oxidation of the 4H-SiC substrate and eliminate the strain of β-Ga_(2)O_(3)(100)film,which further reduces the nucleation energy and en-larges the conversion barrier.Meanwhile,the AlN buffer layer can increase the oxygen vacancy formation energy and decrease the oxygen vacancy concentration of β-Ga_(2)O_(3)(100)film.Consequently,the solar-blind photodetector based on the oriented film exhibits the outstanding detectivity of 1.22×10^(12) Jones and photo-to-dark current ratio of 1.11×10^(5),which are the highest among the reported β-Ga_(2)O_(3) solar-blind photodetector on the SiC substrate.Our results offer in-depth insights into the preferred orientation growth mechanism,and provide an effective way to design high-quality β-Ga_(2)O_(3)(100)orientation film and high-performance solar-blind photodetector.展开更多
In this paper,we investigate the interfacial behavior of a thin,penny-shaped,one-dimensional(1D)hexagonal functionally graded(FG)piezoelectric quasicrystal(PQC)film bonded on a temperature-dependent elastic substrate ...In this paper,we investigate the interfacial behavior of a thin,penny-shaped,one-dimensional(1D)hexagonal functionally graded(FG)piezoelectric quasicrystal(PQC)film bonded on a temperature-dependent elastic substrate under thermal and electrical loads.The problem is modeled as axisymmetric based on the membrane theory,with the peeling stress and bending moment being disregarded.A potential theory method,combined with the Hankel transform technique,is utilized to derive the displacement field on the substrate surface.With perfect interfacial bonding assumption,an integral equation governing the phonon interfacial shear stress is formulated and numerically solved by the Chebyshev polynomials.Explicit expressions are derived for the interfacial shear stress,the internal stresses within the PQC film and the substrate,the axial strain,and the stress intensity factors(SIFs).Numerical simulations are conducted to investigate the effects of the film's aspect ratio,material inhomogeneity,material mismatch,and temperature-dependent material properties on its mechanical response.The results provide insights for the functional design and reliability assessment of FG PQC film/substrate systems.展开更多
ZnO films with c -axis parallel to the substrate are reported.ZnO films are synthesized by solid-source chemical vapor deposition,a novel CVD technique,using zinc acetate dihydrate (solid) as the source material.The p...ZnO films with c -axis parallel to the substrate are reported.ZnO films are synthesized by solid-source chemical vapor deposition,a novel CVD technique,using zinc acetate dihydrate (solid) as the source material.The properties are characterized by X-ray diffraction,atomic force microscopy and transmission spectra.The parallel oriented ZnO films with mixed orientation for (100) and (110) planes are achieved on glass at the substrate temperature of 200℃ and the source temperature of 280℃,and a qualitative explanation is given for the forming of the mixed orientation.AFM images show that the surface is somewhat rough for the parallel oriented ZnO films.The transmission spectrum exhibits a high transmittance of about 85% in the visible region and shows an optical band gap about 3.25eV at room temperature.展开更多
The characteristics of hot filament chemical vapor deposition（HFCVD） diamond films are significantly influenced by the deposition parameters, such as the substrate temperature, total pressure and carbon concentratio...The characteristics of hot filament chemical vapor deposition（HFCVD） diamond films are significantly influenced by the deposition parameters, such as the substrate temperature, total pressure and carbon concentration. Orthogonal experiments were introduced to study the comprehensive effects of such three parameters on diamond films deposited on WC-Co substrates. Field emission scanning electron microscopy, atomic force microscopy and Raman spectrum were employed to analyze the morphology, growth rate and composition of as-deposited diamond films. The morphology varies from pyramidal to cluster features with temperature decreasing. It is found that the low total pressure is suitable for nano-crystalline diamond films growth. Moreover, the substrate temperature and total pressure have combined influence on the growth rate of the diamond films.展开更多
A Ni layer with a thickness of about 100 nm was sputtered on Cu substrates,followed by an ultrasonic seeding with nanodiamond suspension.High-quality diamond film with its crystalline grains close to thermal equilibri...A Ni layer with a thickness of about 100 nm was sputtered on Cu substrates,followed by an ultrasonic seeding with nanodiamond suspension.High-quality diamond film with its crystalline grains close to thermal equilibrium shape was deposited on Cu substrates by hot-filament chemical vapor deposition（HF-CVD）,and the sp2 carbon content was less than 5.56%.The nucleation and growth of diamond film were investigated by micro-Raman spectroscopy,scanning electron microscopy,and X-ray diffraction.The results show that the nucleation density of diamond on the Ni-modified Cu substrates is 10 times higher than that on blank Cu substrates.The enhancement mechanism of the nucleation kinetics by Ni modification layer results from two effects：namely,the nanometer rough Ni-modified surface shows an improved absorption of nanodiamond particles that act as starting points for the diamond nucleation during HF-CVD process;the strong catalytic effect of the Ni-modified surface causes the formation of graphite layer that acts as an intermediate to facilitate diamond nucleation quickly.展开更多
An immobilized Cu2O/g-C3N4 heterojunction film was successfully made on an FTO substrate by electrophoretic deposition of g-C3N4 on a Cu2O thin film.The photoelectrochemical（PEC） performance for water splitting by t...An immobilized Cu2O/g-C3N4 heterojunction film was successfully made on an FTO substrate by electrophoretic deposition of g-C3N4 on a Cu2O thin film.The photoelectrochemical（PEC） performance for water splitting by the Cu2O/g-C3N4 film was better than pure g-C3N4 and pure Cu2O film.Under-0.4 V external bias and visible light irradiation,the photocurrent density and PEC hydrogen evolution efficiency of the optimized Cu2O/g-C3N4 film was-1.38 mA/cm^2 and 0.48 mL h^-1 cm^-2,respectively.The enhanced PEC performance of Cu2O/g-C3N4 was attributed to the synergistic effect of light coupling and a matching energy band structure between g-C3N4 and Cu2O as well as the external bias.展开更多
Large area diamond films were fabricated on copper substrates by a multi-step process comprised of electroplating Cu-diamond composite layer on Cu substrate, plating a Cu layer to fix the protruding diamond particles,...Large area diamond films were fabricated on copper substrates by a multi-step process comprised of electroplating Cu-diamond composite layer on Cu substrate, plating a Cu layer to fix the protruding diamond particles, and depositing continuous diamond film on composite interlayer by hot-filament chemical vapor deposition （HFCVD）. The interface characteristics, internal stress and adhesion strength were investigated by scanning electron microscopy, Raman analysis and indentation test. The results show that the continuous film without cracks is successfully obtained. The microstructure of the film is a mixture of large cubo-octahedron grains grown from homo-epitaxial growth and small grains with （111） apparent facets grown from lateral second nuclei. The improved adhesion between diamond film and substrate results from the deep anchoring of the diamond particles in the Cu matrix and the low residual stress in the film.展开更多
Deposition parameters that have great influences on hot filament chemical vapor deposition (HFCVD) diamond films growth on inner hole surfaces of WC?Co substrates mainly include the substrate temperature (t), carbon c...Deposition parameters that have great influences on hot filament chemical vapor deposition (HFCVD) diamond films growth on inner hole surfaces of WC?Co substrates mainly include the substrate temperature (t), carbon content (φ), total pressure (p) and total mass flow (F). Taguchi method was used for the experimental design in order to study the combined effects of the four parameters on the properties of as-deposited diamond films. A new figure-of-merit (FOM) was defined to assess their comprehensive performance. It is clarified thatt,φandp all have significant and complicated effects on the performance of the diamond film and the FOM, which also present some differences as compared with the previous studies on CVD diamond films growth on plane or external surfaces. Aiming to deposit HFCVD diamond films with the best comprehensive performance, the key deposition parameters were finally optimized as:t=830 °C,φ=4.5%,p=4000 Pa,F=800 mL/min.展开更多
基金support from the National Natural Science Foundation of China(No.11172022)the support by the China Postdoctoral Science Foundation(No.2013M530907)the National Natural Science Foundation of China(No.11302039)
文摘The conventional analytical method of predicting strain in a thin film under bending is restricted to the uniform material assumption, while in flexible electronics, the film/substrate structure is widely used with mismatched material properties taken into account. In this paper,a piecewise model is proposed to analyze the axial strain in a thin film of flexible electronics with the shear modification factor and principle of virtual work. The excellent agreement between analytical prediction and finite element results indicates that the model is capable of predicting the strain of the film/substrate structure in flexible electronics, whose mechanical stability and electrical performance is dependent on the strain state in the thin film.
基金This research was supported by the National Natural Science Foundation of China(11772335,21622304,61674045,and 21203038)by the Ministry of Science and Technology(MOST)of China(2016YFA0200700).Z.H.Cheng was supported by the Distinguished Technical Talents Project and the Youth Innovation Promotion Association of Chinese Academy of Sciences.
文摘In an indentation test,the effective Young's modulus of a film/substrate bilayer heterostructure varies with the indentation depth,a phenomenon known as the substrate effect.In previous studies investigating this,only the Young's modulus of the film was unknown.Once the effective Young's modulus of a film/substrate structure is determined at a given contact depth,the Young's modulus of the film can be uniquely determined,i.e.,there is a one-to-one relation between the Young's modulus of the film and the film/substrate effective Young's modulus.However,at times it is extremely challenging or even impossible to measure the film thickness.Furthermore,the precise definition of the layer/film thickness for a two-dimensional material can be problematic.In the current study,therefore,the thickness of the film and its Young's modulus are treated as two unknowns that must be determined.Unlike the case with one unknown,there are infinite combinations of film thickness and Young's modulus which can yield the same effective Young's modulus for the film/substrate.An inverse problem is formulated and solved to extract the Young's modulus and thickness of the film from the indentation depth-load curve.The accuracy and robustness of the inverse problem-solving method are also demonstrated.
基金Supported by the National Basic Research Program of China under Grant Nos 2010CB631005,2011CBG0C105the National Natural Science Foundation of China under Grant Nos 11172151,11232008,11072152,11272175the Specialized Research Fund for the Doctoral Program of Higher Education under Grant No 20090002110048.Tsinghua University Initiative Scientific Research Program。
文摘Perfect Archimedes spiral cracks at micrometer scales are found in a colloid film of several hundred nanometers in thickness coated on a glass substrate.To explain the formation of this kind of spiral crack,the relation between the geometrical properties of the Archimedes spiral and the growth kinematics of the spiral cracks are analyzed.Meanwhile,the initiation and propagation of the spiral cracks are speculated upon logically from the specific material system based on sufficient evidence.In addition,we introduce a new cracking phenomenon and provide an insight into the new mechanism for crack propagation in soft material nano films coated on stiff substrates.
基金Supported by the National Natural Science Foundation of China under Grant No 10574073.
文摘Transient thermal grating method is used to measure the thermal diffusivity of absorbing films deposited on transparent substrates. According to periodically modulated dielectric constant variations and thermoelastic deformations of the thin films caused by the transient thermal gratings, an improved optical diffraction theory is presented. In the experiment, the probing laser beam reflectively diffracted by the thermal grating is measured by a photomultiplier at different grating fringe spaces. The thermal diffusivity of the film can be evaluated by fitting the theoretical calculations of diffraction signals to the experimental measured data. The validity of the method is tested by measuring the thermal diffusivities of absorbing ZnO films deposited on glass substrates.
基金supported by the National Natural Science Foundation of China(Nos.12072209,U21A20430,12192211,12472155)the S&T Program of Hebei(225676162GH).
文摘We study the axisymmetric frictionless indentation problem of a piezoelectric semiconductor(PSC)thin film perfectly bonded to a semi-infinite isotropic elastic substrate by a rigid and insulating spherical indenter.The Hankel integral transformation is first employed to derive the general solutions for the governing differential equations of the PSC film and elastic substrate.Then,using the boundary and interface conditions,the complicated indentation problem is reduced to numerically solve a Fredholm integral equation of the second kind.Numerical results are given to demonstrate the effects of semiconducting property,film thickness as well as Young’s modulus and Poisson’s ratio of the substrate on the indentation responses.The obtained findings will contribute to the establishment of indentation experiments for PSC film/substrate systems.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 51901163 and 12104171)the Fundamental Research Funds for the Central Universities (Grant No. 2021XXJS025)the Natural Science Foundation of Hubei Province (Grants No. 2024AFB888)。
文摘Electronics over flexible substrates offer advantages of flexibility, portability and low cost, and promising applications in the areas of energy, information, defense science and medical service. In recent years, tremendous progress has been witnessed in the development of flexible wearable devices that can be potentially massively deployed. Of particular interest are intelligent wearable devices, such as sensors and storage cells, which can be integrated by flexible magnetoelectronic devices based on magnetic thin films. To examine this further, the magnetic properties of FeNi thin films with different thicknesses grown on flexible graphene substrate are investigated at room temperature. The coercivity increases with increasing thicknesses of FeNi thin film, which can be attributed to the increase of grain size and decrease of surface roughness. Moreover, the thickness modulated magnetic property shows a magnetic anisotropy shift increase with varying thicknesses of FeNi thin film by using measurements based on ferromagnetic resonance, which further enhances the resonance frequency. In addition, the resonance peak is quite stable after bending it for ten cycles. The result is promising for the future design of flexible magnetoelectronic devices.
基金supported by the National Natural Science Foundation of China(Grant Nos.52125204,52250281,52422209,92163210,and U21A2066)the Na-tional Key Research and Development Program of China(Grant Nos.2024YFA1208601,2022YFB3807602,and 2022YFB3807604).
文摘Doped HfO_(2)as an emerging ferroelectric material,holds considerable promise for non-volatile memory applications.Epitaxial growth of doped HfO_(2)thin films is widely adopted as an effective technique for revealing the intrinsic ferroelectric properties.In this study,based on systematic structural,chemical and electrical investigations,the influences of Mn doping and substrate orientation on ferroelectric properties of Mn-doped HfO_(2)epitaxial thin films are investigated.The results demonstrate that Mn-doped HfO_(2)thin films with orthorhombic phase can be epitaxially grown along[111]out-of-plane direction on both SrTiO_(3)(001)and(110)substrates,and 10%Mn-doping significantly stabilizes the orthorhombic polar phase and enhances the ferroelectric polarization.Interestingly,compared to the films on SrTiO_(3)(001)substrate,the better crystallinity and reduction of oxygen vacancy amount in Mn-doped HfO_(2)films grown on the SrTiO_(3)(110)substrate are observed,which enhance the remanent polarization and reduce the coercive field.It provides an effective approach for the controllable regulation of defects and the enhancement of intrinsic ferroelectricity in HfO_(2)-based materials.
基金This work was supported by the Youth Project of Hunan Provincial Department of Education(Grant No.22B0334)the Bridge and Tunnel Engineering Innovation Project of Changsha University of Science&Technology(Grant No.11ZDXK11)and the Practical Innovation and Entrepreneurship Capacity Improvement Plan of Changsha University of Science and Technology(Grant No.CLSJCX23029).
文摘Organisms have evolved a strain limiting mechanism,reflected as a non-linear elastic constitutive,to prevent large deformations from threatening soft tissue integrity.Compared with linear elastic substrates,the wrinkle of films on non-linear elastic substrates has received less attention.In this article,a unique wrinkle evolution of the film-substrate system with a J-shaped non-linear stress-strain relation is reported.The result shows that a concave hexagonal array pattern is formed with the shrinkage strain of the film-substrate systems developing.As the interconnection of hexagonal arrays,a unit cell ridge network appears with properties such as chirality and helix.The subparagraph maze pattern formed with high compression is mainly composed of special single-cell ridge networks such as spiral single cores,chiral double cores,and combined multi-cores.This evolutionary model is highly consistent with the results of experiments,and it also predicts wrinkle morphology that has not yet been reported.These findings can serve as a novel explanation for the surface wrinkle of biological soft tissue,as well as provide references for the preparation of artificial biomaterials and programmable soft matter.
基金supported by the National Natural Science Foundation of China(Grant No.11804288)the Natural Science Foundation of Henan(Grant No.232300420120)。
文摘The Casimir pressure plays an important role in the adhesion stability of nanofilms at submicro scales.In this work,the Casimir pressure of peptide films deposited on a layered substrate is investigated.Three types of semi-infinite substrates,i.e.,silica,silicon and gold,are considered.The buffer layer between the peptide film and substrate consists of silicon or silica.The switching sign of the Casimir pressure can be controlled in a region ranging from about 130 nm to 1000 nm,depending on the thickness of the buffer layer and the substrate.The results suggest that the critical thickness of peptide films for Casimir equilibrium increases(or decreases)by increasing the thickness of the silicon(or silica)buffer film.The influences of wetting and electrolyte screening on the Casimir pressure are also investigated.Our finding provides a theoretical guide for the adhesion stability of peptide films in organic electronics.
基金financially supported by the National Natural Science Foundation of China (No. 22076075)Guangdong Provincial Key Laboratory of Soil and Groundwater Pollution Control (No. 2023B1212060002)+1 种基金the Key Program of Fundamental Research from the Shenzhen Science and Technology Innovation Commission (No. JCYJ20220818100218039)the General Program of Fundamental Research from the Shenzhen Science and Technology Innovation Commission (No. JCY20230807092500001)。
文摘Thin-film nanocomposite(TFN) membranes have garnered considerable attention for their potential to improve separation performance by incorporating nanomaterials. However, challenges such as these materials' uneven distribution and aggregation have hindered practical applications. While prior studies have largely concentrated on modifying nanosheets for compatibility with polymer matrices, the role of substrate pore size in influencing nanosheet distribution has been overlooked. In this work, MoS_(2) nanosheets were dispersed in an aqueous phase to fabricate TFN membranes, investigating the effect of substrate pore size relative to the nanosheets. By systematically varying the particle size of MoS_(2) and the pore size of the substrate, we reveal how these factors impact material distribution and structural uniformity within the membranes. Our findings reveal that larger substrate pores allow the MoS_(2)-containing monomer solution to infiltrate more effectively, minimizing nanosheet aggregation. This enhances membrane performance by promoting better dispersion. Our results underscore the importance of considering the relative size of substrate pores and nanosheets in TFN membrane design, providing a pathway to improved material integration and higher membrane efficiency.
基金Research Project of Shenzhen Science and Technology Innovation Committee(JCYJ20180306170801080)。
文摘Amorphous Ga_(2)O_(3)(a-Ga_(2)O_(3))thin films were prepared on flexible polyimide,rigid quartz glass,and Si substrates via radio frequency magnetron sputtering at room temperature.The effect of oxygen/Ar flow rate ratio on the structure,optical property,surface morphology,and chemical bonding properties of the a-Ga_(2)O_(3) films was investigated.Results show that the average optical transmittance of the a-Ga_(2)O_(3) films is over 80%within the wavelength range of 300-2000 nm.The extracted optical band gap of the a-Ga_(2)O_(3) films is increased from 4.97 eV to 5.13 eV with the increase in O_(2)/Ar flow rate ratio from 0 to 0.25,due to the decrease in concentration of oxygen vacancy defects in the film.Furthermore,the optical refractive index and surface roughness of the a-Ga_(2)O_(3) films are optimized when the O_(2)/Ar flow rate ratio reaches 0.25.X-ray photoelectron spectroscopy analysis also shows that the proportion of oxygen vacancies(VO)and Ga-O chemical bonds in the O 1s peak is gradually decreased with the increase in O_(2)/Ar flow rate ratio from 0 to 0.25,proving that increasing the O_(2)/Ar flow rate ratio during film growth can reduce the concentration of oxygen vacancy defects in a-Ga_(2)O_(3) films.In this case,a-Ga_(2)O_(3) with optimal properties can be obtained.This work provides a research basis for high-performance flexible and rigid deep ultraviolet solar-blind detection devices based on a-Ga_(2)O_(3) films.
基金the AECS for its financial support of this study
文摘Organosilicone thin films were prepared through plasma polymerization(pp)in a plasma enhance chemical vapour deposition(PECVD)system,utilizing hexamethyldisilazane(HMDSN)as a monomer precursor,at varying distances(25 mm,35 mm,45 mm,55 mm,and 65 mm)from the plasma source to the substrate.Research has examined how the distance between the substrate and plasma source impacts the properties of thin films,including their thickness,surface morphology,and photoluminescence(PL).It was discovered that as the distance increased,both film thickness and PL intensity also increased.Additionally,the film was observed to be more uniform and smoother when deposited 45 mm below the plasma source.
基金supported by the National Key Research and Development Program of China(No.2021YFA0715600)the National Natural Science Foundation of China(Nos.62274125,52192611)+2 种基金the Guangdong Basic and Applied Basic Research Fund(No.2023A1515030084)the Key Research and Development Program of Shaanxi Province(Grant No.2024GX-YBXM-410)the fund of the State Key Laboratory of Solidification Processing in NWPU(No.SKLSP202220).
文摘Optimizing the orientation of β-Ga_(2)O_(3) has emerged as an effective strategy to design high-performance β-Ga_(2)O_(3) device,but the orientation growth mechanism and approach have not been revealed yet.Herein,by employing AlN buffer layer,the highly preferred orientation of β-Ga_(2)O_(3)(100)film rather than(-201)film is realized on 4H-SiC substrate at low sputtering power and temperature.Because β-Ga_(2)O_(3)(100)film exhibits a slower growth speed than(-201)film,the former possesses the higher dangling bond density and the lower nucleation energy,and a large conversion barrier exists between these two ori-entations.Moreover,the AlN buffer layer can suppress the surface oxidation of the 4H-SiC substrate and eliminate the strain of β-Ga_(2)O_(3)(100)film,which further reduces the nucleation energy and en-larges the conversion barrier.Meanwhile,the AlN buffer layer can increase the oxygen vacancy formation energy and decrease the oxygen vacancy concentration of β-Ga_(2)O_(3)(100)film.Consequently,the solar-blind photodetector based on the oriented film exhibits the outstanding detectivity of 1.22×10^(12) Jones and photo-to-dark current ratio of 1.11×10^(5),which are the highest among the reported β-Ga_(2)O_(3) solar-blind photodetector on the SiC substrate.Our results offer in-depth insights into the preferred orientation growth mechanism,and provide an effective way to design high-quality β-Ga_(2)O_(3)(100)orientation film and high-performance solar-blind photodetector.
基金Project supported by the National Natural Science Foundation of China(Nos.11902293 and 12272353)。
文摘In this paper,we investigate the interfacial behavior of a thin,penny-shaped,one-dimensional(1D)hexagonal functionally graded(FG)piezoelectric quasicrystal(PQC)film bonded on a temperature-dependent elastic substrate under thermal and electrical loads.The problem is modeled as axisymmetric based on the membrane theory,with the peeling stress and bending moment being disregarded.A potential theory method,combined with the Hankel transform technique,is utilized to derive the displacement field on the substrate surface.With perfect interfacial bonding assumption,an integral equation governing the phonon interfacial shear stress is formulated and numerically solved by the Chebyshev polynomials.Explicit expressions are derived for the interfacial shear stress,the internal stresses within the PQC film and the substrate,the axial strain,and the stress intensity factors(SIFs).Numerical simulations are conducted to investigate the effects of the film's aspect ratio,material inhomogeneity,material mismatch,and temperature-dependent material properties on its mechanical response.The results provide insights for the functional design and reliability assessment of FG PQC film/substrate systems.
文摘ZnO films with c -axis parallel to the substrate are reported.ZnO films are synthesized by solid-source chemical vapor deposition,a novel CVD technique,using zinc acetate dihydrate (solid) as the source material.The properties are characterized by X-ray diffraction,atomic force microscopy and transmission spectra.The parallel oriented ZnO films with mixed orientation for (100) and (110) planes are achieved on glass at the substrate temperature of 200℃ and the source temperature of 280℃,and a qualitative explanation is given for the forming of the mixed orientation.AFM images show that the surface is somewhat rough for the parallel oriented ZnO films.The transmission spectrum exhibits a high transmittance of about 85% in the visible region and shows an optical band gap about 3.25eV at room temperature.
基金Project(2012ZX04003-031)supported by the National Science and Technology Major Project,China
文摘The characteristics of hot filament chemical vapor deposition（HFCVD） diamond films are significantly influenced by the deposition parameters, such as the substrate temperature, total pressure and carbon concentration. Orthogonal experiments were introduced to study the comprehensive effects of such three parameters on diamond films deposited on WC-Co substrates. Field emission scanning electron microscopy, atomic force microscopy and Raman spectrum were employed to analyze the morphology, growth rate and composition of as-deposited diamond films. The morphology varies from pyramidal to cluster features with temperature decreasing. It is found that the low total pressure is suitable for nano-crystalline diamond films growth. Moreover, the substrate temperature and total pressure have combined influence on the growth rate of the diamond films.
基金Project(20110933K) supported by the State Key Laboratory of Powder Metallurgy,ChinaProject(2012QNZT002) supported by the Freedom Explore Program of Central South University,ChinaProject(CSUZC2012024) supported by the Open-End Fund for the Valuable and Precision Instruments of Central South University,China
文摘A Ni layer with a thickness of about 100 nm was sputtered on Cu substrates,followed by an ultrasonic seeding with nanodiamond suspension.High-quality diamond film with its crystalline grains close to thermal equilibrium shape was deposited on Cu substrates by hot-filament chemical vapor deposition（HF-CVD）,and the sp2 carbon content was less than 5.56%.The nucleation and growth of diamond film were investigated by micro-Raman spectroscopy,scanning electron microscopy,and X-ray diffraction.The results show that the nucleation density of diamond on the Ni-modified Cu substrates is 10 times higher than that on blank Cu substrates.The enhancement mechanism of the nucleation kinetics by Ni modification layer results from two effects：namely,the nanometer rough Ni-modified surface shows an improved absorption of nanodiamond particles that act as starting points for the diamond nucleation during HF-CVD process;the strong catalytic effect of the Ni-modified surface causes the formation of graphite layer that acts as an intermediate to facilitate diamond nucleation quickly.
基金supported by the National Natural Science Foundation of China (21173088)the Science and Technology Project of Guangdong Province (2014A030312007, 2015A050502012, 2016A010104013)+1 种基金the China Postdoctoral Science Foundation (2016M592493)the Open Research Fund of Hunan Key Laboratory of Applied Environmental Photocatalysis (CCSU-XT-06),Changsha University~~
文摘An immobilized Cu2O/g-C3N4 heterojunction film was successfully made on an FTO substrate by electrophoretic deposition of g-C3N4 on a Cu2O thin film.The photoelectrochemical（PEC） performance for water splitting by the Cu2O/g-C3N4 film was better than pure g-C3N4 and pure Cu2O film.Under-0.4 V external bias and visible light irradiation,the photocurrent density and PEC hydrogen evolution efficiency of the optimized Cu2O/g-C3N4 film was-1.38 mA/cm^2 and 0.48 mL h^-1 cm^-2,respectively.The enhanced PEC performance of Cu2O/g-C3N4 was attributed to the synergistic effect of light coupling and a matching energy band structure between g-C3N4 and Cu2O as well as the external bias.
基金Projects(51071070,51271079)supported by the National Natural Science Foundation of ChinaProject(NCET-11-0156)supported by New Century Excellent Talents in University,China
文摘Large area diamond films were fabricated on copper substrates by a multi-step process comprised of electroplating Cu-diamond composite layer on Cu substrate, plating a Cu layer to fix the protruding diamond particles, and depositing continuous diamond film on composite interlayer by hot-filament chemical vapor deposition （HFCVD）. The interface characteristics, internal stress and adhesion strength were investigated by scanning electron microscopy, Raman analysis and indentation test. The results show that the continuous film without cracks is successfully obtained. The microstructure of the film is a mixture of large cubo-octahedron grains grown from homo-epitaxial growth and small grains with （111） apparent facets grown from lateral second nuclei. The improved adhesion between diamond film and substrate results from the deep anchoring of the diamond particles in the Cu matrix and the low residual stress in the film.
基金Projects(51275302,51005154)supported by the National Natural Science Foundation of China
文摘Deposition parameters that have great influences on hot filament chemical vapor deposition (HFCVD) diamond films growth on inner hole surfaces of WC?Co substrates mainly include the substrate temperature (t), carbon content (φ), total pressure (p) and total mass flow (F). Taguchi method was used for the experimental design in order to study the combined effects of the four parameters on the properties of as-deposited diamond films. A new figure-of-merit (FOM) was defined to assess their comprehensive performance. It is clarified thatt,φandp all have significant and complicated effects on the performance of the diamond film and the FOM, which also present some differences as compared with the previous studies on CVD diamond films growth on plane or external surfaces. Aiming to deposit HFCVD diamond films with the best comprehensive performance, the key deposition parameters were finally optimized as:t=830 °C,φ=4.5%,p=4000 Pa,F=800 mL/min.
