Silicon nanowires(SiNWs)with diameter distributions ranging from 80 to 350 nm were prepared by electrochemical reduction of Ni/SiO2 in molten CaCl2.The effect of the content of nickel additives on the morphology of pr...Silicon nanowires(SiNWs)with diameter distributions ranging from 80 to 350 nm were prepared by electrochemical reduction of Ni/SiO2 in molten CaCl2.The effect of the content of nickel additives on the morphology of produced silicon was investigated.Large quantities of SiNWs are obtained by the electrochemical reduction of Ni/SiO2 blocks with SiO2 to Ni molar ratio of 20 and 10.Nickel additives repress the growth of irregular branches and promote longitudinal growth of SiNWs.Wire morphologies and surfaces are influenced by the electrolysis temperature.SiNWs become thicker with the increase of the electrolysis temperature.The optimum temperature to prepare single crystal SiNWs with high aspect ratio and extraordinary surface quality seems to be 1173 K.The amorphous layer of the silicon nanowire is thinner compared to the SiNWs obtained from the pure SiO2 pellets.The produced SiNWs show a photoluminescence emission peak at about 758 nm at room temperature.This work demonstrates the potentiality for the electrochemical reduction process to obtain large quantities of SiNWs with high quality.展开更多
Interdigitated back contact（IBC） solar cells can achieve a very high efficiency due to its less optical losses. But IBC solar cells demand for high quality passivation of the front surface. In this paper, a polycrys...Interdigitated back contact（IBC） solar cells can achieve a very high efficiency due to its less optical losses. But IBC solar cells demand for high quality passivation of the front surface. In this paper, a polycrystalline silicon/SiO_2 stack structure as front surface field to passivate the front surface of IBC solar cells is proposed. The passivation quality of this structure is investigated by two dimensional simulations. Polycrystalline silicon layer and SiO_2 layer are optimized to get the best passivation quality of the IBC solar cell. Simulation results indicate that the doping level of polycrystalline silicon should be high enough to allow a very thin polycrystalline silicon layer to ensure an effective passivation and small optical losses at the same time. The thickness of SiO_2 should be neither too thin nor too thick, and the optimal thickness is 1.2 nm.Furthermore, the lateral transport properties of electrons are investigated, and the simulation results indicate that a high doping level and conductivity of polycrystalline silicon can improve the lateral transportation of electrons and then the cell performance.展开更多
We studied the local structure and properties of six-fold coordinated silicon(Si[6]) in BaOSiO2-P2O5 glasses. Nuclear magnetic resonance(NMR) and Raman spectroscopy revealed the existence of sixfold coordinated silico...We studied the local structure and properties of six-fold coordinated silicon(Si[6]) in BaOSiO2-P2O5 glasses. Nuclear magnetic resonance(NMR) and Raman spectroscopy revealed the existence of sixfold coordinated silicon species and network former units(NFUs) in the BaO-SiO2-P2O5 glasses. The glass transition temperature(Tg), which was measured by differential scanning calorimetry, increased rapidly along with the increase of SiO2 from 0 to 10 mol%, then declined and finally increased again, which showed a "Z" trend along with the increase of SiO2 while the density of the glasses showed the opposite trend. When the addition of SiO2 is 16 mol%, Tg decreased to an extremely low value(807.9 K). Besides, the Vickers indentation hardness(Hv) had been significantly enhanced from 4.66 to 6.63 GPa by adding 16 mol% SiO2. Furthermore, the liquid fragility index(m) of the glasses declined slowly firstly and then increased rapidly when the amount of SiO2 is greater than 13 mol%.展开更多
Cz n-type Si (100) samples with and without a top SiO2 layer were implanted with 40 keV helium ions at the same dose of 5×1016 cm-2. Cross-sectional transmission electron microscopy (XTEM) and thermal desorption ...Cz n-type Si (100) samples with and without a top SiO2 layer were implanted with 40 keV helium ions at the same dose of 5×1016 cm-2. Cross-sectional transmission electron microscopy (XTEM) and thermal desorption spectroscopy (THDS) were used to study the thermal evolution of cavities upon and helium thermal release, respectively. XTEM results show that the presence of the top SiO2 layer could suppress the thermal growth of cavities mainly formed in the region close to the SiO2/Si interface, which leads to the reduction in both the cavity band and cavity density. THDS results reveal that the top oxide layer could act as an effective barrier for the migration of helium atoms to the surface, and it thus gives rise to the formation of more overpresurrized bubbles and to the occurrence of a third release peak located at about 1100 K. The results were qualitively discussed by considering the role of the oxide surface layer in defect migration and evolution upon annealing.展开更多
A silicon on reflector (SOR) substrate containing a thin crystal silicon layer and a buried Si/SiO 2 Bragg reflector is reported. The substrate, which is applied to optoelectronic devices, is fabricated by using Si...A silicon on reflector (SOR) substrate containing a thin crystal silicon layer and a buried Si/SiO 2 Bragg reflector is reported. The substrate, which is applied to optoelectronic devices, is fabricated by using Si based sol gel sticking and smart cut techniques. The reflectivity of the SOR substrate is close to unity at 1 3μm's wavelength under the normal incidence.展开更多
Effect of SiO 2 content and sintering process on the composition and properties of Pure Carbon Reaction Bonded Silicon Carbide (PCRBSC) ceramics prepared with C-SiO 2 green body by infiltrating silicon was presented...Effect of SiO 2 content and sintering process on the composition and properties of Pure Carbon Reaction Bonded Silicon Carbide (PCRBSC) ceramics prepared with C-SiO 2 green body by infiltrating silicon was presented.The infiltrating mechanism of C-SiO 2 preform was also explored.The experimental results indicate that the shaping pressure increases with the addition of SiO 2 to the preform,and the pore size of the body turned finer and distributed in a narrower range,which is beneficial to decreasing the residual silicon content in the sintered materials and to avoiding shock off,thus increasing the conversion rate of SiC.SiO 2 was deoxidized by carbon at a high temperature and the gaseous SiO and CO produced are the main reason to the crack of the body at an elevated temperature.If the green body is deposited at 1800℃ in vacuum before infiltration crack will not be produced in the preform and fully dense RBSC can be obtained.The ultimate material has the following properties:a density of 3.05-3.12g/cm3,a strength of 580±32MPa and a hardness of (HRA)91-92.3.展开更多
Macroporous silicon formed by photoanodic etching with high aspect ratio and large effective surface is one of the promising materials for the development of 2D photonic structures. We fabricated nanocoatings of CdTe,...Macroporous silicon formed by photoanodic etching with high aspect ratio and large effective surface is one of the promising materials for the development of 2D photonic structures. We fabricated nanocoatings of CdTe, ZnO, CdS surface nanocrystals and SiO2 layers on macroporous silicon surface. The near-IR optical absorption was investigated and well-separated oscillations with giant amplitude were observed in the spectral ranges of surface level absorption. This process is because of resonance electron scattering on the surface impurity states with the difference between two resonance energies equal to the Wannier-Stark ladder. Macroporous silicon structures with SiO2 nanolayers and CdS nanocrystals are proposed to enhance the photoluminescence of CdS nanoparticles with quantum yield 28%. Addition functionalization of 2D macroporous silicon is a result of the high-pressure oxidation. The structural SiO2 reorganization to orthorhombic phase increases the concentration of paramagnetic Pb centers, EPR signal amplitude and GHz radiation absorption.展开更多
A new method for fabricating ordered porous silicon is reported. A two-dimensional silica nanosphere array is used as a template with a hydrofluoric acid-hydrogen peroxide solution for etching the nanospheres. The ini...A new method for fabricating ordered porous silicon is reported. A two-dimensional silica nanosphere array is used as a template with a hydrofluoric acid-hydrogen peroxide solution for etching the nanospheres. The initial diameter and distribution of the holes in the resulting porous silicon layer are determined by the size and distribution of the silica nanospheres. The corrosion time can be used to control the depths of the holes. It is found that the presence of a SiO2 layer, formed by the oxidation of the rough internal surface of the hole, is the primary reason allowing the corrosion to proceed. Ultraviolet reflection and thermal conductivity measurements show that the diameter and distribution of the holes have a great influence on properties of the porous silicon.展开更多
Based on the surface passivation of n-type silicon in a silicon drift detector(SDD), we propose a new passivation structure of SiO2/Al2O3/SiO2 passivation stacks. Since the SiO2 formed by the nitric-acid-oxidation-of-...Based on the surface passivation of n-type silicon in a silicon drift detector(SDD), we propose a new passivation structure of SiO2/Al2O3/SiO2 passivation stacks. Since the SiO2 formed by the nitric-acid-oxidation-of-silicon(NAOS)method has good compactness and simple process, the first layer film is formed by the NAOS method. The Al2O3 film is also introduced into the passivation stacks owing to exceptional advantages such as good interface characteristic and simple process. In addition, for requirements of thickness and deposition temperature, the third layer of the SiO2 film is deposited by plasma enhanced chemical vapor deposition(PECVD). The deposition of the SiO2 film by PECVD is a low-temperature process and has a high deposition rate, which causes little damage to the device and makes the SiO2 film very suitable for serving as the third passivation layer. The passivation approach of stacks can saturate dangling bonds at the interface between stacks and the silicon substrate, and provide positive charge to optimize the field passivation of the n-type substrate.The passivation method ultimately achieves a good combination of chemical and field passivations. Experimental results show that with the passivation structure of SiO2/Al2O3/SiO2, the final minority carrier lifetime reaches 5223 μs at injection of 5×10^(15) cm^(-3). When it is applied to the passivation of SDD, the leakage current is reduced to the order of nA.展开更多
We investigate the properties of light emission from amorphous-Si：H/SiO2 and nc-Si/SiO2 multilayers （MLs）. The size dependence of light emission is well exhibited when the a-Si：H sublayer thickness is thinner than...We investigate the properties of light emission from amorphous-Si：H/SiO2 and nc-Si/SiO2 multilayers （MLs）. The size dependence of light emission is well exhibited when the a-Si：H sublayer thickness is thinner than 4 nm and the interface states are well passlvated by hydrogen. For the nc-Si/Si02 MLs, the oxygen modified interface states and nanocrystalline silicon play a predominant role in the properties of light emission. It is found that the light emission from nc-Si/SiO2 is in agreement with the model of interface state combining with quantum confinement when the size of nc-Si is smaller than 4 nm. The role of hydrogen and oxygen is discussed in detail.展开更多
Porous silicon nitride ceramics（Si3N4） were fabricated by pressureless sintering using different particle size of silicon nitride powder.Lu2O3 was used as sintering additive.According to phase relationships in the t...Porous silicon nitride ceramics（Si3N4） were fabricated by pressureless sintering using different particle size of silicon nitride powder.Lu2O3 was used as sintering additive.According to phase relationships in the ternary system Si3N4-SiO2-Lu2O3,porous Si3N4 ceramics with different phase composition were designed through the change of the content of SiO2 which was formed by the oxidation at 800℃ in air.Porous Si3N4 with different phase compositions was obtained after sintering at 1800℃ in N2atmosphere.A small content of SiO2 favored the formation of secondary phase Lu4Si2O7N2,while large content of SiO2 favored the formation of secondary phase Lu2Si2O7 and Si2N2O.Porous Si3N4 ceramics with secondary phase Lu4Si2O7N2 had a flexural strength of 207 MPa,while that with secondary phase Si2N2O and Lu2Si2O7 had lower flexural strength.展开更多
By means of scanning electron microscope(SEM)and high voltage electron microscope(HVEM)we have observed and analysed morphology and micro-structure of silicon oxide film with different thickness formed on(111)silicon ...By means of scanning electron microscope(SEM)and high voltage electron microscope(HVEM)we have observed and analysed morphology and micro-structure of silicon oxide film with different thickness formed on(111)silicon monocrystal under dry oxygen atmosphere at 1100℃.Compared with their oxidation kinetic curves consisted of three stages,we suggested a mechanism on forming silicon oxide film.According to electron and X-ray diffraction analyses the silicon oxide films consisted of silica with different crystal structure.We also have discussed a stacking fault and a dislocation formed in the Si-Sio_2 interface region simulaneously forming silicon oxide film.展开更多
Room temperature operated sensor for detection of alcohol vapours in low ppm range based on TiO_2 functionalized nano-porous silicon（PSi） is demonstrated. The effect of functionalization by TiO_2 on PSi is investiga...Room temperature operated sensor for detection of alcohol vapours in low ppm range based on TiO_2 functionalized nano-porous silicon（PSi） is demonstrated. The effect of functionalization by TiO_2 on PSi is investigated using SEM, EDX, Raman spectroscopy, XRD and contact angle measurements. Sensing is accomplished by measuring change in resistance of the sensing layer using Cr-Au inter-digitatedelectrode（IDE） structure formed on top of the functionalized PSi layer. The sensors were tested for volatile organic compounds（VOCs） and water vapours in the wide range of 5–500 ppm concentration at room temperature. Functionalization of the nanostructured PSi by sputter deposited TiO_2 results in significant enhancement of sensitivity and inverse change in selectivity. PSi sensors have displayed strong response to water vapours whereas after functionalization, selective sensing to ethanol is depicted. Minimum detection by PSi sensors is portrayed at 100 ppm and that of functionalized sensors is at 10 ppm. Sensing mechanism is explained on the basis of surfaces and structures of both PSi and TiO_2. This study incites the importance of surface treatment of PSi for tuning the sensing properties and is useful in the development of selective alcohol sensors.展开更多
基金financially supported by the National Natural Science Foundation of China(No.51404032 and No.51504032)the National High Technology Research and Development Program of China(No.2013AA050904)
文摘Silicon nanowires(SiNWs)with diameter distributions ranging from 80 to 350 nm were prepared by electrochemical reduction of Ni/SiO2 in molten CaCl2.The effect of the content of nickel additives on the morphology of produced silicon was investigated.Large quantities of SiNWs are obtained by the electrochemical reduction of Ni/SiO2 blocks with SiO2 to Ni molar ratio of 20 and 10.Nickel additives repress the growth of irregular branches and promote longitudinal growth of SiNWs.Wire morphologies and surfaces are influenced by the electrolysis temperature.SiNWs become thicker with the increase of the electrolysis temperature.The optimum temperature to prepare single crystal SiNWs with high aspect ratio and extraordinary surface quality seems to be 1173 K.The amorphous layer of the silicon nanowire is thinner compared to the SiNWs obtained from the pure SiO2 pellets.The produced SiNWs show a photoluminescence emission peak at about 758 nm at room temperature.This work demonstrates the potentiality for the electrochemical reduction process to obtain large quantities of SiNWs with high quality.
基金supported by the National Natural Science Foundation of China(Grant Nos.11104319,11274346,51202285,61234005,51172268,51602340,61274059,and 51402347)the Solar Energy Action Plan of Chinese Academy of Sciences(Grant Nos.Y1YT064001,Y1YF034001,and Y2YF014001)+2 种基金the Graduate and College Student’s Innovative Project(Grant No.YC2016-X19)the Project of Beijing Municipal Science and Technology Commission(Grant No.Z151100003515003)the Opening Project of Key Laboratory of Microelectronics Devices&Integrated Technology,Institute of Microelectronics,Chinese Academy of Sciences
文摘Interdigitated back contact（IBC） solar cells can achieve a very high efficiency due to its less optical losses. But IBC solar cells demand for high quality passivation of the front surface. In this paper, a polycrystalline silicon/SiO_2 stack structure as front surface field to passivate the front surface of IBC solar cells is proposed. The passivation quality of this structure is investigated by two dimensional simulations. Polycrystalline silicon layer and SiO_2 layer are optimized to get the best passivation quality of the IBC solar cell. Simulation results indicate that the doping level of polycrystalline silicon should be high enough to allow a very thin polycrystalline silicon layer to ensure an effective passivation and small optical losses at the same time. The thickness of SiO_2 should be neither too thin nor too thick, and the optimal thickness is 1.2 nm.Furthermore, the lateral transport properties of electrons are investigated, and the simulation results indicate that a high doping level and conductivity of polycrystalline silicon can improve the lateral transportation of electrons and then the cell performance.
基金Funded by National Natural Science Foundation of China(Nos.51772223,51372180)
文摘We studied the local structure and properties of six-fold coordinated silicon(Si[6]) in BaOSiO2-P2O5 glasses. Nuclear magnetic resonance(NMR) and Raman spectroscopy revealed the existence of sixfold coordinated silicon species and network former units(NFUs) in the BaO-SiO2-P2O5 glasses. The glass transition temperature(Tg), which was measured by differential scanning calorimetry, increased rapidly along with the increase of SiO2 from 0 to 10 mol%, then declined and finally increased again, which showed a "Z" trend along with the increase of SiO2 while the density of the glasses showed the opposite trend. When the addition of SiO2 is 16 mol%, Tg decreased to an extremely low value(807.9 K). Besides, the Vickers indentation hardness(Hv) had been significantly enhanced from 4.66 to 6.63 GPa by adding 16 mol% SiO2. Furthermore, the liquid fragility index(m) of the glasses declined slowly firstly and then increased rapidly when the amount of SiO2 is greater than 13 mol%.
文摘Cz n-type Si (100) samples with and without a top SiO2 layer were implanted with 40 keV helium ions at the same dose of 5×1016 cm-2. Cross-sectional transmission electron microscopy (XTEM) and thermal desorption spectroscopy (THDS) were used to study the thermal evolution of cavities upon and helium thermal release, respectively. XTEM results show that the presence of the top SiO2 layer could suppress the thermal growth of cavities mainly formed in the region close to the SiO2/Si interface, which leads to the reduction in both the cavity band and cavity density. THDS results reveal that the top oxide layer could act as an effective barrier for the migration of helium atoms to the surface, and it thus gives rise to the formation of more overpresurrized bubbles and to the occurrence of a third release peak located at about 1100 K. The results were qualitively discussed by considering the role of the oxide surface layer in defect migration and evolution upon annealing.
文摘A silicon on reflector (SOR) substrate containing a thin crystal silicon layer and a buried Si/SiO 2 Bragg reflector is reported. The substrate, which is applied to optoelectronic devices, is fabricated by using Si based sol gel sticking and smart cut techniques. The reflectivity of the SOR substrate is close to unity at 1 3μm's wavelength under the normal incidence.
文摘Effect of SiO 2 content and sintering process on the composition and properties of Pure Carbon Reaction Bonded Silicon Carbide (PCRBSC) ceramics prepared with C-SiO 2 green body by infiltrating silicon was presented.The infiltrating mechanism of C-SiO 2 preform was also explored.The experimental results indicate that the shaping pressure increases with the addition of SiO 2 to the preform,and the pore size of the body turned finer and distributed in a narrower range,which is beneficial to decreasing the residual silicon content in the sintered materials and to avoiding shock off,thus increasing the conversion rate of SiC.SiO 2 was deoxidized by carbon at a high temperature and the gaseous SiO and CO produced are the main reason to the crack of the body at an elevated temperature.If the green body is deposited at 1800℃ in vacuum before infiltration crack will not be produced in the preform and fully dense RBSC can be obtained.The ultimate material has the following properties:a density of 3.05-3.12g/cm3,a strength of 580±32MPa and a hardness of (HRA)91-92.3.
文摘Macroporous silicon formed by photoanodic etching with high aspect ratio and large effective surface is one of the promising materials for the development of 2D photonic structures. We fabricated nanocoatings of CdTe, ZnO, CdS surface nanocrystals and SiO2 layers on macroporous silicon surface. The near-IR optical absorption was investigated and well-separated oscillations with giant amplitude were observed in the spectral ranges of surface level absorption. This process is because of resonance electron scattering on the surface impurity states with the difference between two resonance energies equal to the Wannier-Stark ladder. Macroporous silicon structures with SiO2 nanolayers and CdS nanocrystals are proposed to enhance the photoluminescence of CdS nanoparticles with quantum yield 28%. Addition functionalization of 2D macroporous silicon is a result of the high-pressure oxidation. The structural SiO2 reorganization to orthorhombic phase increases the concentration of paramagnetic Pb centers, EPR signal amplitude and GHz radiation absorption.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10804026 and 51101049the Natural Science Foundation of Hebei Province under Grant Nos A2013205101 and A2014205051the Hebei Talent Cultivation Foundation under Grant No A201400119
文摘A new method for fabricating ordered porous silicon is reported. A two-dimensional silica nanosphere array is used as a template with a hydrofluoric acid-hydrogen peroxide solution for etching the nanospheres. The initial diameter and distribution of the holes in the resulting porous silicon layer are determined by the size and distribution of the silica nanospheres. The corrosion time can be used to control the depths of the holes. It is found that the presence of a SiO2 layer, formed by the oxidation of the rough internal surface of the hole, is the primary reason allowing the corrosion to proceed. Ultraviolet reflection and thermal conductivity measurements show that the diameter and distribution of the holes have a great influence on properties of the porous silicon.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51602340,51702355,and 61674167)the Natural Science Foundation of Beijing Municipality of China(Grant No.4192064)+1 种基金the National Key Research Program of China(Grant Nos.2018YFB1500500 and 2018YFB1500200)the JKW Project of China(Grant No.31512060106)。
文摘Based on the surface passivation of n-type silicon in a silicon drift detector(SDD), we propose a new passivation structure of SiO2/Al2O3/SiO2 passivation stacks. Since the SiO2 formed by the nitric-acid-oxidation-of-silicon(NAOS)method has good compactness and simple process, the first layer film is formed by the NAOS method. The Al2O3 film is also introduced into the passivation stacks owing to exceptional advantages such as good interface characteristic and simple process. In addition, for requirements of thickness and deposition temperature, the third layer of the SiO2 film is deposited by plasma enhanced chemical vapor deposition(PECVD). The deposition of the SiO2 film by PECVD is a low-temperature process and has a high deposition rate, which causes little damage to the device and makes the SiO2 film very suitable for serving as the third passivation layer. The passivation approach of stacks can saturate dangling bonds at the interface between stacks and the silicon substrate, and provide positive charge to optimize the field passivation of the n-type substrate.The passivation method ultimately achieves a good combination of chemical and field passivations. Experimental results show that with the passivation structure of SiO2/Al2O3/SiO2, the final minority carrier lifetime reaches 5223 μs at injection of 5×10^(15) cm^(-3). When it is applied to the passivation of SDD, the leakage current is reduced to the order of nA.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60508009, 90301009, 60471021, 50472066, and 10574069, and the State Key Basic Research Programme of China under Grant No 2006CB932202.
文摘We investigate the properties of light emission from amorphous-Si：H/SiO2 and nc-Si/SiO2 multilayers （MLs）. The size dependence of light emission is well exhibited when the a-Si：H sublayer thickness is thinner than 4 nm and the interface states are well passlvated by hydrogen. For the nc-Si/Si02 MLs, the oxygen modified interface states and nanocrystalline silicon play a predominant role in the properties of light emission. It is found that the light emission from nc-Si/SiO2 is in agreement with the model of interface state combining with quantum confinement when the size of nc-Si is smaller than 4 nm. The role of hydrogen and oxygen is discussed in detail.
基金the State Key Laboratory of Solidification Processing in NWPU(No. KB200920)the Program for New Century Excellent Talents in University
文摘Porous silicon nitride ceramics（Si3N4） were fabricated by pressureless sintering using different particle size of silicon nitride powder.Lu2O3 was used as sintering additive.According to phase relationships in the ternary system Si3N4-SiO2-Lu2O3,porous Si3N4 ceramics with different phase composition were designed through the change of the content of SiO2 which was formed by the oxidation at 800℃ in air.Porous Si3N4 with different phase compositions was obtained after sintering at 1800℃ in N2atmosphere.A small content of SiO2 favored the formation of secondary phase Lu4Si2O7N2,while large content of SiO2 favored the formation of secondary phase Lu2Si2O7 and Si2N2O.Porous Si3N4 ceramics with secondary phase Lu4Si2O7N2 had a flexural strength of 207 MPa,while that with secondary phase Si2N2O and Lu2Si2O7 had lower flexural strength.
文摘By means of scanning electron microscope(SEM)and high voltage electron microscope(HVEM)we have observed and analysed morphology and micro-structure of silicon oxide film with different thickness formed on(111)silicon monocrystal under dry oxygen atmosphere at 1100℃.Compared with their oxidation kinetic curves consisted of three stages,we suggested a mechanism on forming silicon oxide film.According to electron and X-ray diffraction analyses the silicon oxide films consisted of silica with different crystal structure.We also have discussed a stacking fault and a dislocation formed in the Si-Sio_2 interface region simulaneously forming silicon oxide film.
基金supported by the Department of Science and Technology (DST), Ministry of Science and Technology, Govt. of India, under the INSPIRE Faculty grant IFA 12-ENG-13MHRD, Government of India for providing the financial assistantship for research
文摘Room temperature operated sensor for detection of alcohol vapours in low ppm range based on TiO_2 functionalized nano-porous silicon（PSi） is demonstrated. The effect of functionalization by TiO_2 on PSi is investigated using SEM, EDX, Raman spectroscopy, XRD and contact angle measurements. Sensing is accomplished by measuring change in resistance of the sensing layer using Cr-Au inter-digitatedelectrode（IDE） structure formed on top of the functionalized PSi layer. The sensors were tested for volatile organic compounds（VOCs） and water vapours in the wide range of 5–500 ppm concentration at room temperature. Functionalization of the nanostructured PSi by sputter deposited TiO_2 results in significant enhancement of sensitivity and inverse change in selectivity. PSi sensors have displayed strong response to water vapours whereas after functionalization, selective sensing to ethanol is depicted. Minimum detection by PSi sensors is portrayed at 100 ppm and that of functionalized sensors is at 10 ppm. Sensing mechanism is explained on the basis of surfaces and structures of both PSi and TiO_2. This study incites the importance of surface treatment of PSi for tuning the sensing properties and is useful in the development of selective alcohol sensors.
