The development of optoelectronic technologies demands photodetectors with miniaturization,broadband operation,high sensitivity,and low power consumption.Although 2D van der Waals(vd W)heterostructures are promising c...The development of optoelectronic technologies demands photodetectors with miniaturization,broadband operation,high sensitivity,and low power consumption.Although 2D van der Waals(vd W)heterostructures are promising candidates due to their built-in electric fields,ultrafast photocarrier separation,and tunable bandgaps,defect states limit their performance.Therefore,the modulation of the optoelectronic properties in such heterostructures is imperative.Surface charge transfer doping(SCTD)has emerged as a promising strategy for non-destructive modulation of electronic and optoelectronic characteristics in two-dimensional materials.In this work,we demonstrate the construction of high-performance p-i-n vertical heterojunction photodetectors through SCTD of MoTe_(2)/ReS_(2)heterostructure using p-type F_(4)-TCNQ.Systematic characterization reveals that the interfacial doping process effectively amplifies the built-in electric field,enhancing photogenerated carrier separation efficiency.Compared to the pristine heterojunction device,the doped photodetector exhibits remarkable visible to nearinfrared(635-1064 nm)performance.Particularly under 1064 nm illumination at zero bias,the device achieves a responsivity of 2.86 A/W and specific detectivity of 1.41×10^(12)Jones.Notably,the external quantum efficiency reaches an exceptional value of 334%compared to the initial 11.5%,while maintaining ultrafast response characteristics with rise/fall times of 11.6/15.6μs.This work provides new insights into interface engineering through molecular doping for developing high-performance vd W optoelectronic devices.展开更多
The microstructure, dielectric properties and chemical state of Ti element on BaTi_4O_9 (f)/(0.64 BaTi_4O_9-0.36BaPr_2Ti_4O_(12)) composites sample surface were characterized by X-ray diffraction (XRD), Transmission e...The microstructure, dielectric properties and chemical state of Ti element on BaTi_4O_9 (f)/(0.64 BaTi_4O_9-0.36BaPr_2Ti_4O_(12)) composites sample surface were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), LCR meter method and X-ray photoelectron spectroscopy (XPS). The results show that the system is composed of BaTi_4O_9 and BaPr_2Ti_4O_(12) two phases. Pr ions are distributed in the BaWi_4O_9 grains and the segregation of Pr ions was observed on the grain boundaries of BaTi_4O_9/BaTi_4O_9. The content of Ti^(3+) and Ti^(2+) decrease in the BPT system composites due to the addition of BaTi_4O_9 fibers, which improved the dielectric properties of the system. BPT10 sample with 10% BaTi_4O_9 fibers, has the best dielectric properties in the system, its ε_r = 64, tan δ= 1×10^(-4)(at 1 MHz) , and it may be a potential candidate for microwave dielectric ceramics.展开更多
Compared with bulk-silicon technology, silicon-on-insulator (SOI) technology possesses many advan-tages but it is inevitable that the buried silicon dioxide layer also thermally insulates the metal – oxide – silicon...Compared with bulk-silicon technology, silicon-on-insulator (SOI) technology possesses many advan-tages but it is inevitable that the buried silicon dioxide layer also thermally insulates the metal – oxide – silicon field-effect transistors (MOSFETs) from the bulk due to the low thermal conductivity. One of the alternative insulator to replace the buried oxide layer is aluminum nitride (AlN), which has a thermal conductivity that is about 200 times higher than that of SiO2 (320 W·m ? 1·K? 1 versus 1.4 W·m? 1·K? 1). To investigate the self-heating effects of small-size MOSFETs fabricated on silicon-on-aluminum nitride (SOAN) substrate, a two-dimensional numerical analysis is performed by using a device simulator called MEDICI run on a Solaris workstation to simulate the electri-cal characteristics and temperature distribution by comparing with those of bulk and standard SOI MOSFETs. Our study suggests that AlN is a suitable alternative to silicon dioxide as a buried dielectric in SOI and expands the appli-cations of SOI to high temperature conditions.展开更多
The doping effects of rare earth oxides Ho_2O_3 and Er_2O_3 on dielectric properties of BaTiO_3-based ceramics were studied. After adding rare earth elements, grain growth in this system was inhibited and the grain si...The doping effects of rare earth oxides Ho_2O_3 and Er_2O_3 on dielectric properties of BaTiO_3-based ceramics were studied. After adding rare earth elements, grain growth in this system was inhibited and the grain size was reduced evidently which realized the fine-grained effect. In this system, the trivalent oxides Ho_2O_3 and Er_2O_3 were added to BaTiO_3 ceramics. The rare earth oxides do not enter into inner lattice totally to replace A or B sites. Some of additives can improve dielectric strength by forming nonferroelectric phases, and the rest maintained at grain boundaries controls overgrowth of grains. The dielectric constant at room temperature is increased up to 3000 and the curve of TCC becomes flat. Meanwhile, the dielectric strength E_b becomes higher.展开更多
Two-dimensional(2D)2H-MoTe2 is a promising semiconductor because of its small bandgap,strong absorption,and low thermal conductivity.In this paper,we systematically study the optical and excitonic properties of atomic...Two-dimensional(2D)2H-MoTe2 is a promising semiconductor because of its small bandgap,strong absorption,and low thermal conductivity.In this paper,we systematically study the optical and excitonic properties of atomically thin 2H-MoTe2(1–5 layers).Due to the fact that the optical contrast and Raman spectra of 2H-MoTe2 with different thicknesses exhibit distinctly different behaviors,we establish a quantitative method by using optical images and Raman spectra to directly identify the layers of 2H-MoTe2 thin films.Besides,excitonic states and binding energy in monolayer/bilayer 2H-MoTe2 are measured by temperature-dependent photoluminescence(PL)spectroscopy.At temperature T=3.3 K,we can observe an exciton emission at^1.19 eV and trion emission at^1.16 eV for monolayer 2H-MoTe2.While at room temperature,the exciton emission and trion emission both disappear for their small binding energy.We determine the exciton binding energy to be 185 meV(179 meV),trion binding energy to be 20 meV(18 me V)for the monolayer(bilayer)2H-MoTe2.The thoroughly studies of the excitonic states in atomically thin 2H-MoTe2 will provide guidance for future practical applications.展开更多
The paper presents a prototype of virtual decoder of the transport stream＇s system target decoder （T-STD）. By connecting the coding model and decoding model, and feeding the overflow of decoding buffer back to cont...The paper presents a prototype of virtual decoder of the transport stream＇s system target decoder （T-STD）. By connecting the coding model and decoding model, and feeding the overflow of decoding buffer back to control coding, we have got a self-adaptive coding model, and propose an algorithm of muhiplexing multiple elementary streams to a transport stream based on the principle of virtual buffer controlling strategy. The transport stream （TS） which uses this method passes the test of software unzipping and set top-box （STB） playing, and all of the analyzing parameters which are detected by code analyzer accord with the standard of MPEG-2. Some problems that playing time becomes longer and mul tiple TS streaming can not be fit for all the players are also analyzed.展开更多
A surface mounted device （SMD） microwave ceramic band-pass filter for mobile communication with a new coupling structure is reported in this paper. In this filter, the external and internal coupling structures are f...A surface mounted device （SMD） microwave ceramic band-pass filter for mobile communication with a new coupling structure is reported in this paper. In this filter, the external and internal coupling structures are fabricated on an alumina substrate and both resonators and coupling structures are placed into a metal house to cut off its radiation. The relationship between the coupling structures and the performance of the filter is analyzed by high frequency structure software （HFSS） and the filter with a center frequency of 836.5 MHz, bandwidth of 40.0 MHz, pass-band ripple of 0.1 dB and insertion loss of 1.5 dB has been successfully designed and fabricated. The measured results show a good agreement with the simulation results.展开更多
CaBi_(4)Ti_(4)O_(15)(CBT)-based Aurivillius high-temperature piezoceramics with different Sb-Mn co-doping amounts were synthesized via the conventional sintering technique.The influences of doping amount on the produc...CaBi_(4)Ti_(4)O_(15)(CBT)-based Aurivillius high-temperature piezoceramics with different Sb-Mn co-doping amounts were synthesized via the conventional sintering technique.The influences of doping amount on the product were studied via their crystal structure,microstructure,and piezoelectric performance.It is found that an appropriate Sb-Mn co-doping amount can effectively optimize the crystal structure and decrease the oxygen vacancy concentration in CBT ceramics,leading to enhanced electrical properties.Optimized electrical performance with a high Curie temperature(TC)of 792℃and a remarkable piezoelectric coefficient(d33)of 25 p C/N were achieved at a doping amount(x)of 0.05.Furthermore,this ceramic is found to exhibit an excellent thermal stability,with d33 retaining 88%of its original value after annealing at 600℃for 2 h.Moreover,this ceramic shows a high electrical resistivity(ρ)of 1.35×10^(8)Ω·cm with a small dielectric loss(tanδ)of 1.7%at 400℃.Because of such outstanding piezoelectric performance,it is believed that these Sb-Mn co-doped CBT ceramics could be potential candidates for high-temperature piezoelectric applications.展开更多
In this Letter, we firstly, to the best of our knowledge, demonstrated the influence of pre-pulse current and delay time on the intensity of a discharge pumped Ne-like Ar soft X-ray laser operating at 46.9 nm by emplo...In this Letter, we firstly, to the best of our knowledge, demonstrated the influence of pre-pulse current and delay time on the intensity of a discharge pumped Ne-like Ar soft X-ray laser operating at 46.9 nm by employing an alumina capillary having an inner diameter of 4.8 mm. Specifically, the delay time was changed from 8 to 520 μs in small intervals. The pre-discharge current was increased from 25 A to 250 A through small steps, while keeping the main discharge current constant. Usually, a small pre-discharge current is applied to an Ar-filled capillary to attain a plasma column having sufficient pre-ionization before the injection of the main current. The predischarge current of 140 A was declared the best current to obtain lasing with a 4.8 mm diameter capillary.The laser spots were captured at best time delays for the pre-discharge currents of 25, 45, 80, 140, and250 A, which support the experimental results. We observed that by applying the pre-discharge current of140 A, the laser spot exhibits small divergence, higher symmetry, and uniformity, which is clear evidence of strong amplification. The laser spot obtained at 140 A is cylindrically symmetric and has a better structure than those reported by all other groups in the literature. Hence, the laser spot indicates that the laser beam is highly focusable and beneficial for the applications of the 46.9 nm laser. Results of this Letter might open a new way to enhance applications of a 46.9 nm capillary discharge soft X-ray laser.展开更多
Optoelectronic properties of MoSe2 are modulated by controlled annealing in air.Characterizations by Raman spectroscopy and XPS demonstrate the introduction of oxygen defects.Considerable increase in electron and hole...Optoelectronic properties of MoSe2 are modulated by controlled annealing in air.Characterizations by Raman spectroscopy and XPS demonstrate the introduction of oxygen defects.Considerable increase in electron and hole mobilities reveals the highly improved electron and hole transport.Furthermore,the photocurrent is enhanced by nearly four orders of magnitudes under 7 nW laser exposure after annealing.The remarkable enhancement in the photoresponse is attributed to an increase in hole trapping centers and a reduction in resistance.Furthermore,the annealed photodetector shows a fast time response on the order of 10 ms and responsivity of 3×10^(4) A/W.展开更多
Different sp^(3) content diamond-like carbon films are deposited on to highly n-doped Si(111)substrates by a new plasma deposition technique-filtered arc deposition.Their electron field emission properties are studied...Different sp^(3) content diamond-like carbon films are deposited on to highly n-doped Si(111)substrates by a new plasma deposition technique-filtered arc deposition.Their electron field emission properties are studied by using a simple diode structure.It is showed that the turn-on field is decreased and field emission current density is increased with the increasing sp3 content(75-80%,80-83%,and 88-90%)of the films.Field emission current of 0.1μA from the three samples was detected under the electric field of 10.1,5.6,and 2.9 V/μm and emission current density of 4.4,15.2,and 43.2μA/cm^(2),respectively,under 14.3 V/μm.Fowler-Nordheim(F-N)plots of the three samples nearly show of lineaity indicating that electron field emission obeys F-N theory.展开更多
This paper presents a new encryption embedded processor aimed at the application requirement of wireless sensor network （WSN）. The new encryption embedded processor not only offers Rivest Shamir Adlemen （RSA）, Adv...This paper presents a new encryption embedded processor aimed at the application requirement of wireless sensor network （WSN）. The new encryption embedded processor not only offers Rivest Shamir Adlemen （RSA）, Advanced Encryption Standard （AES）, 3 Data Encryption Standard （3 DES） and Secure Hash Algorithm 1 （SHA - 1 ） security engines, but also involves a new memory encryption scheme. The new memory encryption scheme is implemented by a memory encryption cache （MEC）, which protects the confidentiality of the memory by AES encryption. The experi- ments show that the new secure design only causes 1.9% additional delay on the critical path and cuts 25.7% power consumption when the processor writes data back. The new processor balances the performance overhead, the power consumption and the security and fully meets the wireless sensor environment requirement. After physical design, the new encryption embedded processor has been successfully tape-out.展开更多
This paper explores an energy-efficient pulsed ultra-wideband（UWB） radio-frequency（RF） front-end chip fabricated in 0.18-μm CMOS technology, including a transmitter, receiver, and fractional synthesizer. The tran...This paper explores an energy-efficient pulsed ultra-wideband（UWB） radio-frequency（RF） front-end chip fabricated in 0.18-μm CMOS technology, including a transmitter, receiver, and fractional synthesizer. The transmitter adopts a digital offset quadrature phase-shift keying（O-QPSK） modulator and passive direct-phase multiplexing technology, which are energy-and hardware-efficient, to enhance the data rate for a given spectrum.A passive mixer and a capacitor cross-coupled（CCC） source-follower driving amplifier（DA） are also designed for the transmitter to further reduce the low power consumption. For the receiver, a power-aware low-noise amplifier（LNA） and a quadrature mixer are applied. The LNA adopts a CCC boost common-gate amplifier as the input stage, and its current is reused for the second stage to save power. The mixer uses a shared amplification stage for the following passive IQ mixer. Phase noise suppression of the phase-locked loop（PLL） is achieved by utilizing an even-harmonics-nulled series-coupled quadrature oscillator（QVCO） and an in-band noise-aware charge pump（CP） design. The transceiver achieves a measured data rate of 0.8 Gbps with power consumption of 16 m W and31.5 m W for the transmitter and the receiver, respectively. The optimized integrated phase noise of the PLL is0.52° at 4.025 GHz.展开更多
This paper presents a super performance bandgap voltage reference for DC-DC converter with adjustable output. it generates a wide range of voltage reference ranging from sub- 1V to 1,221 7 V and has a low temperature ...This paper presents a super performance bandgap voltage reference for DC-DC converter with adjustable output. it generates a wide range of voltage reference ranging from sub- 1V to 1,221 7 V and has a low temperature coefficient of 2.3 × 10 ^5/K over the temperature variation using the current feedback and resistive subdivision. In addition, the power supply rejection ration of the proposed bandgap voltage reference is 78 dB. When supply voltage varies from 2.5 V to 6 V, output VREF is 1,221 685±0.055 mV.展开更多
Hydrogen-free high sp^3 content amorphous diamond (AD) films are deposited on three different substrates——Au-coated Si (Au/Si), Ti-coated Si (Ti/Si) and Si wafers. Electron field emission properties and fluorescent ...Hydrogen-free high sp^3 content amorphous diamond (AD) films are deposited on three different substrates——Au-coated Si (Au/Si), Ti-coated Si (Ti/Si) and Si wafers. Electron field emission properties and fluorescent displays of the above AD films are studied by using a sample diode structure. The compositional profile of the interfaces of AD/Ti/Si and AD/Si is examined by using secondary ions mass spectroscopy (SIMS). Because of the reaction and interdiffusion between Ti and C, the formation of a thin TiC intermediate layer is possible between AD film and Ti/Si substrate. The field emission properties of AD/Ti/Si are sufficiently improved, especially its uniformity. A field emission density of 0.352 mA/cm^2 is obtained under an electric field of 19.7 V/μm. The value is much more than that of AD/Au/Si and AD/Si under the same electric field.展开更多
Surface charge transfer doping has been widely utilized to tune the electronic and optical properties of semiconductor photodetectors based on low-dimensional materials.Although many studies have been conducted on the...Surface charge transfer doping has been widely utilized to tune the electronic and optical properties of semiconductor photodetectors based on low-dimensional materials.Although many studies have been conducted on the performance(response time,responsivity,etc.)of doped photodetectors and their mechanisms,they merely examined a specific thickness and did not systematically explore the dependence of doping effects on the number of layers.This work performs a series of investigations on ReS_(2)photodetectors with different numbers of layers and demonstrates that the p-dopant tetrafluorotetracyanoquinodimethane(F_(4)-TCNQ)converts the deep trap states into recombination centers for few-layer ReS_(2)and induces a vertical p-n junction for thicker ReS_(2).A response time of 200 ms is observed in the decorated 2-layer ReS_(2)photodetector,more than two orders of magnitude faster than the response of the pristine photodetector,due to the disappearance of deep trap states.A current rectification ratio of 30 in the F_(4)-TCNQ-decorated sandwiched ReS_(2)device demonstrates the formation of a vertical p-n junction in a thicker ReS_(2)device.The responsivity is as high as 2,000 A/W owing to the strong carrier separation of the p-n junction.Different thicknesses of ReS_(2)enable switching of the prominent operating mechanism between transforming deep trap states into recombination centers and forming a vertical p-n junction.The thicknessdependent doping effect of a two-dimensional material serves as a new mechanism and provides a scheme toward improving the performance of other semiconductor devices,especially optical and electronic devices based on low-dimensional materials.展开更多
Dielectric capacitors with high capacitive energy storage are urgently needed to meet the growing demand for high-performance energy storage devices.Herein,a novel lead-free Sr_(5)BiTi_(3)Nb_(7)O_(30)(SBTN)tungsten br...Dielectric capacitors with high capacitive energy storage are urgently needed to meet the growing demand for high-performance energy storage devices.Herein,a novel lead-free Sr_(5)BiTi_(3)Nb_(7)O_(30)(SBTN)tungsten bronze relaxor ferroelectric ceramic is prepared and explored for potential energy storage applications.A high recoverable energy density Wrec(~3.72 J/cm^(3))and ultrahigh efficiencyη(~94.2%)at 380 kV/cm are achieved simultaneously.Both Wrec andηexhibit superior stabilities against temperature(30-140°C),cycles(100-105)and frequency(1-500 Hz).In addition,a high current density of 796 A/cm^(2) and a large power density of 71.7 MW/cm^(3) are achieved,together with good thermal endurance and fatigue resistance.These results demonstrate that the obtained SBTN ceramic can be deemed as the promising candidates for dielectric capacitor applications.展开更多
Video adaptation is a promising technique to bridge the gap between network status, device capabilities, and user preferences in pervasive media applications. However, conventional adaptation frameworks based on eithe...Video adaptation is a promising technique to bridge the gap between network status, device capabilities, and user preferences in pervasive media applications. However, conventional adaptation frameworks based on either transcoding or multiple pre-transcoding are not able to accommodate large numbers of users with diversified applications. This paper introduces an intermediate video description called ＂Inter- media＂, which consists of multiple level video signal components, such as texture, motion, and rate control information, as well as some semantic features, such as structural characteristics and Region Of Interest （ROI） information. It is generated off-line and stored in the video server or media gateway. Intermedia is then used to design a novel video adaptation system. The proposed adaptation system quickly and easily generates the required bit stream from Intermedia with very low complexity to fulfill a series of specific adaptation requirements, e.g., bitrate conversion, temporal/spatial resolution reduction, video summarization, ROI browsing, and some multi-level adaptations involving both signal level and semantic level adaptation. The satisfactory performance of such a system demonstrates the effectiveness and efficiency of the proposed video adaptation framework.展开更多
This paper suggests the method for MPEG 2 Transport Stream ( TS ) processing and transmitting over CATV (HFC ). An MPEG 2 TS Generator Card design is presented. The system configuration and the function...This paper suggests the method for MPEG 2 Transport Stream ( TS ) processing and transmitting over CATV (HFC ). An MPEG 2 TS Generator Card design is presented. The system configuration and the functions of the Generator Card are given. The design of hardware and software for the card and some issues are discussed. A practical system of the application of the MPEG 2 TS Generator Card is given. A satisfactory result has been achieved in the application.展开更多
This article proposes a mechanism of low overhead and less runtime, termed dynamic cache resources allocation （DCRA）, which allocates each application with required cache resources. The mechanism collects cache hit-...This article proposes a mechanism of low overhead and less runtime, termed dynamic cache resources allocation （DCRA）, which allocates each application with required cache resources. The mechanism collects cache hit-miss information at runtime and then analyzes the information and decides how many cache resources should be allocated to the current executing application. The amount of cache resources varies dynamically to reduce the total number of misses and energy consumption. The study of several applications from SPEC2000 shows that significant energy saving is achieved for the application based on the DCRA with an average of 39% savings.展开更多
基金financial support from 2024 Domestic Visiting Scholar Program for Teachers'Professional Development in Universities(Grant No.FX2024022)National Natural Science Foundation of China(Grant No.61904043)。
文摘The development of optoelectronic technologies demands photodetectors with miniaturization,broadband operation,high sensitivity,and low power consumption.Although 2D van der Waals(vd W)heterostructures are promising candidates due to their built-in electric fields,ultrafast photocarrier separation,and tunable bandgaps,defect states limit their performance.Therefore,the modulation of the optoelectronic properties in such heterostructures is imperative.Surface charge transfer doping(SCTD)has emerged as a promising strategy for non-destructive modulation of electronic and optoelectronic characteristics in two-dimensional materials.In this work,we demonstrate the construction of high-performance p-i-n vertical heterojunction photodetectors through SCTD of MoTe_(2)/ReS_(2)heterostructure using p-type F_(4)-TCNQ.Systematic characterization reveals that the interfacial doping process effectively amplifies the built-in electric field,enhancing photogenerated carrier separation efficiency.Compared to the pristine heterojunction device,the doped photodetector exhibits remarkable visible to nearinfrared(635-1064 nm)performance.Particularly under 1064 nm illumination at zero bias,the device achieves a responsivity of 2.86 A/W and specific detectivity of 1.41×10^(12)Jones.Notably,the external quantum efficiency reaches an exceptional value of 334%compared to the initial 11.5%,while maintaining ultrafast response characteristics with rise/fall times of 11.6/15.6μs.This work provides new insights into interface engineering through molecular doping for developing high-performance vd W optoelectronic devices.
文摘The microstructure, dielectric properties and chemical state of Ti element on BaTi_4O_9 (f)/(0.64 BaTi_4O_9-0.36BaPr_2Ti_4O_(12)) composites sample surface were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), LCR meter method and X-ray photoelectron spectroscopy (XPS). The results show that the system is composed of BaTi_4O_9 and BaPr_2Ti_4O_(12) two phases. Pr ions are distributed in the BaWi_4O_9 grains and the segregation of Pr ions was observed on the grain boundaries of BaTi_4O_9/BaTi_4O_9. The content of Ti^(3+) and Ti^(2+) decrease in the BPT system composites due to the addition of BaTi_4O_9 fibers, which improved the dielectric properties of the system. BPT10 sample with 10% BaTi_4O_9 fibers, has the best dielectric properties in the system, its ε_r = 64, tan δ= 1×10^(-4)(at 1 MHz) , and it may be a potential candidate for microwave dielectric ceramics.
基金Supported by the Special Funds for Major State Basic Research Projects (No.G2000036506)the National Natural Science Foundation of China (No. 60476006)
文摘Compared with bulk-silicon technology, silicon-on-insulator (SOI) technology possesses many advan-tages but it is inevitable that the buried silicon dioxide layer also thermally insulates the metal – oxide – silicon field-effect transistors (MOSFETs) from the bulk due to the low thermal conductivity. One of the alternative insulator to replace the buried oxide layer is aluminum nitride (AlN), which has a thermal conductivity that is about 200 times higher than that of SiO2 (320 W·m ? 1·K? 1 versus 1.4 W·m? 1·K? 1). To investigate the self-heating effects of small-size MOSFETs fabricated on silicon-on-aluminum nitride (SOAN) substrate, a two-dimensional numerical analysis is performed by using a device simulator called MEDICI run on a Solaris workstation to simulate the electri-cal characteristics and temperature distribution by comparing with those of bulk and standard SOI MOSFETs. Our study suggests that AlN is a suitable alternative to silicon dioxide as a buried dielectric in SOI and expands the appli-cations of SOI to high temperature conditions.
文摘The doping effects of rare earth oxides Ho_2O_3 and Er_2O_3 on dielectric properties of BaTiO_3-based ceramics were studied. After adding rare earth elements, grain growth in this system was inhibited and the grain size was reduced evidently which realized the fine-grained effect. In this system, the trivalent oxides Ho_2O_3 and Er_2O_3 were added to BaTiO_3 ceramics. The rare earth oxides do not enter into inner lattice totally to replace A or B sites. Some of additives can improve dielectric strength by forming nonferroelectric phases, and the rest maintained at grain boundaries controls overgrowth of grains. The dielectric constant at room temperature is increased up to 3000 and the curve of TCC becomes flat. Meanwhile, the dielectric strength E_b becomes higher.
基金Project supported by the Natural Science Research Projects in Colleges and Universities of Jiangsu Province,China(Grant No.18KJD140003)
文摘Two-dimensional(2D)2H-MoTe2 is a promising semiconductor because of its small bandgap,strong absorption,and low thermal conductivity.In this paper,we systematically study the optical and excitonic properties of atomically thin 2H-MoTe2(1–5 layers).Due to the fact that the optical contrast and Raman spectra of 2H-MoTe2 with different thicknesses exhibit distinctly different behaviors,we establish a quantitative method by using optical images and Raman spectra to directly identify the layers of 2H-MoTe2 thin films.Besides,excitonic states and binding energy in monolayer/bilayer 2H-MoTe2 are measured by temperature-dependent photoluminescence(PL)spectroscopy.At temperature T=3.3 K,we can observe an exciton emission at^1.19 eV and trion emission at^1.16 eV for monolayer 2H-MoTe2.While at room temperature,the exciton emission and trion emission both disappear for their small binding energy.We determine the exciton binding energy to be 185 meV(179 meV),trion binding energy to be 20 meV(18 me V)for the monolayer(bilayer)2H-MoTe2.The thoroughly studies of the excitonic states in atomically thin 2H-MoTe2 will provide guidance for future practical applications.
基金Supported by the Electronics Developing FundProject ( MII[2002]13)
文摘The paper presents a prototype of virtual decoder of the transport stream＇s system target decoder （T-STD）. By connecting the coding model and decoding model, and feeding the overflow of decoding buffer back to control coding, we have got a self-adaptive coding model, and propose an algorithm of muhiplexing multiple elementary streams to a transport stream based on the principle of virtual buffer controlling strategy. The transport stream （TS） which uses this method passes the test of software unzipping and set top-box （STB） playing, and all of the analyzing parameters which are detected by code analyzer accord with the standard of MPEG-2. Some problems that playing time becomes longer and mul tiple TS streaming can not be fit for all the players are also analyzed.
基金Supported by Sino-British Excellent Youth Scholar Foundation (2005362)the Natural Science Foundation of Hubei Province (2008CDB315)
文摘A surface mounted device （SMD） microwave ceramic band-pass filter for mobile communication with a new coupling structure is reported in this paper. In this filter, the external and internal coupling structures are fabricated on an alumina substrate and both resonators and coupling structures are placed into a metal house to cut off its radiation. The relationship between the coupling structures and the performance of the filter is analyzed by high frequency structure software （HFSS） and the filter with a center frequency of 836.5 MHz, bandwidth of 40.0 MHz, pass-band ripple of 0.1 dB and insertion loss of 1.5 dB has been successfully designed and fabricated. The measured results show a good agreement with the simulation results.
基金financial support from the Key Research and Development Project of Zhejiang Province,China(No.2017C01056)。
文摘CaBi_(4)Ti_(4)O_(15)(CBT)-based Aurivillius high-temperature piezoceramics with different Sb-Mn co-doping amounts were synthesized via the conventional sintering technique.The influences of doping amount on the product were studied via their crystal structure,microstructure,and piezoelectric performance.It is found that an appropriate Sb-Mn co-doping amount can effectively optimize the crystal structure and decrease the oxygen vacancy concentration in CBT ceramics,leading to enhanced electrical properties.Optimized electrical performance with a high Curie temperature(TC)of 792℃and a remarkable piezoelectric coefficient(d33)of 25 p C/N were achieved at a doping amount(x)of 0.05.Furthermore,this ceramic is found to exhibit an excellent thermal stability,with d33 retaining 88%of its original value after annealing at 600℃for 2 h.Moreover,this ceramic shows a high electrical resistivity(ρ)of 1.35×10^(8)Ω·cm with a small dielectric loss(tanδ)of 1.7%at 400℃.Because of such outstanding piezoelectric performance,it is believed that these Sb-Mn co-doped CBT ceramics could be potential candidates for high-temperature piezoelectric applications.
基金supported by the National Natural Science Foundation of China (Nos. 61275139 and61875045)。
文摘In this Letter, we firstly, to the best of our knowledge, demonstrated the influence of pre-pulse current and delay time on the intensity of a discharge pumped Ne-like Ar soft X-ray laser operating at 46.9 nm by employing an alumina capillary having an inner diameter of 4.8 mm. Specifically, the delay time was changed from 8 to 520 μs in small intervals. The pre-discharge current was increased from 25 A to 250 A through small steps, while keeping the main discharge current constant. Usually, a small pre-discharge current is applied to an Ar-filled capillary to attain a plasma column having sufficient pre-ionization before the injection of the main current. The predischarge current of 140 A was declared the best current to obtain lasing with a 4.8 mm diameter capillary.The laser spots were captured at best time delays for the pre-discharge currents of 25, 45, 80, 140, and250 A, which support the experimental results. We observed that by applying the pre-discharge current of140 A, the laser spot exhibits small divergence, higher symmetry, and uniformity, which is clear evidence of strong amplification. The laser spot obtained at 140 A is cylindrically symmetric and has a better structure than those reported by all other groups in the literature. Hence, the laser spot indicates that the laser beam is highly focusable and beneficial for the applications of the 46.9 nm laser. Results of this Letter might open a new way to enhance applications of a 46.9 nm capillary discharge soft X-ray laser.
基金Project supported by the National Natural Science Foundation of China(Grant No.61904043)the Natural Science Foundation of Zhejiang Province,China(Grant No.LQ19A040009).
文摘Optoelectronic properties of MoSe2 are modulated by controlled annealing in air.Characterizations by Raman spectroscopy and XPS demonstrate the introduction of oxygen defects.Considerable increase in electron and hole mobilities reveals the highly improved electron and hole transport.Furthermore,the photocurrent is enhanced by nearly four orders of magnitudes under 7 nW laser exposure after annealing.The remarkable enhancement in the photoresponse is attributed to an increase in hole trapping centers and a reduction in resistance.Furthermore,the annealed photodetector shows a fast time response on the order of 10 ms and responsivity of 3×10^(4) A/W.
基金Supported by the 863 Program of the National Science and Technology Committee of China.
文摘Different sp^(3) content diamond-like carbon films are deposited on to highly n-doped Si(111)substrates by a new plasma deposition technique-filtered arc deposition.Their electron field emission properties are studied by using a simple diode structure.It is showed that the turn-on field is decreased and field emission current density is increased with the increasing sp3 content(75-80%,80-83%,and 88-90%)of the films.Field emission current of 0.1μA from the three samples was detected under the electric field of 10.1,5.6,and 2.9 V/μm and emission current density of 4.4,15.2,and 43.2μA/cm^(2),respectively,under 14.3 V/μm.Fowler-Nordheim(F-N)plots of the three samples nearly show of lineaity indicating that electron field emission obeys F-N theory.
文摘This paper presents a new encryption embedded processor aimed at the application requirement of wireless sensor network （WSN）. The new encryption embedded processor not only offers Rivest Shamir Adlemen （RSA）, Advanced Encryption Standard （AES）, 3 Data Encryption Standard （3 DES） and Secure Hash Algorithm 1 （SHA - 1 ） security engines, but also involves a new memory encryption scheme. The new memory encryption scheme is implemented by a memory encryption cache （MEC）, which protects the confidentiality of the memory by AES encryption. The experi- ments show that the new secure design only causes 1.9% additional delay on the critical path and cuts 25.7% power consumption when the processor writes data back. The new processor balances the performance overhead, the power consumption and the security and fully meets the wireless sensor environment requirement. After physical design, the new encryption embedded processor has been successfully tape-out.
基金Project supported by the National Science and Technology Major Project of China(No.2011ZX03004-002-01)
文摘This paper explores an energy-efficient pulsed ultra-wideband（UWB） radio-frequency（RF） front-end chip fabricated in 0.18-μm CMOS technology, including a transmitter, receiver, and fractional synthesizer. The transmitter adopts a digital offset quadrature phase-shift keying（O-QPSK） modulator and passive direct-phase multiplexing technology, which are energy-and hardware-efficient, to enhance the data rate for a given spectrum.A passive mixer and a capacitor cross-coupled（CCC） source-follower driving amplifier（DA） are also designed for the transmitter to further reduce the low power consumption. For the receiver, a power-aware low-noise amplifier（LNA） and a quadrature mixer are applied. The LNA adopts a CCC boost common-gate amplifier as the input stage, and its current is reused for the second stage to save power. The mixer uses a shared amplification stage for the following passive IQ mixer. Phase noise suppression of the phase-locked loop（PLL） is achieved by utilizing an even-harmonics-nulled series-coupled quadrature oscillator（QVCO） and an in-band noise-aware charge pump（CP） design. The transceiver achieves a measured data rate of 0.8 Gbps with power consumption of 16 m W and31.5 m W for the transmitter and the receiver, respectively. The optimized integrated phase noise of the PLL is0.52° at 4.025 GHz.
文摘This paper presents a super performance bandgap voltage reference for DC-DC converter with adjustable output. it generates a wide range of voltage reference ranging from sub- 1V to 1,221 7 V and has a low temperature coefficient of 2.3 × 10 ^5/K over the temperature variation using the current feedback and resistive subdivision. In addition, the power supply rejection ration of the proposed bandgap voltage reference is 78 dB. When supply voltage varies from 2.5 V to 6 V, output VREF is 1,221 685±0.055 mV.
基金Project supported by the National High-Tech Program of China.
文摘Hydrogen-free high sp^3 content amorphous diamond (AD) films are deposited on three different substrates——Au-coated Si (Au/Si), Ti-coated Si (Ti/Si) and Si wafers. Electron field emission properties and fluorescent displays of the above AD films are studied by using a sample diode structure. The compositional profile of the interfaces of AD/Ti/Si and AD/Si is examined by using secondary ions mass spectroscopy (SIMS). Because of the reaction and interdiffusion between Ti and C, the formation of a thin TiC intermediate layer is possible between AD film and Ti/Si substrate. The field emission properties of AD/Ti/Si are sufficiently improved, especially its uniformity. A field emission density of 0.352 mA/cm^2 is obtained under an electric field of 19.7 V/μm. The value is much more than that of AD/Au/Si and AD/Si under the same electric field.
基金This work was supported by the National Natural Science Foundation of China(No.61904043)the Natural Science Foundation of Zhejiang Province(No.LQ19A040009).
文摘Surface charge transfer doping has been widely utilized to tune the electronic and optical properties of semiconductor photodetectors based on low-dimensional materials.Although many studies have been conducted on the performance(response time,responsivity,etc.)of doped photodetectors and their mechanisms,they merely examined a specific thickness and did not systematically explore the dependence of doping effects on the number of layers.This work performs a series of investigations on ReS_(2)photodetectors with different numbers of layers and demonstrates that the p-dopant tetrafluorotetracyanoquinodimethane(F_(4)-TCNQ)converts the deep trap states into recombination centers for few-layer ReS_(2)and induces a vertical p-n junction for thicker ReS_(2).A response time of 200 ms is observed in the decorated 2-layer ReS_(2)photodetector,more than two orders of magnitude faster than the response of the pristine photodetector,due to the disappearance of deep trap states.A current rectification ratio of 30 in the F_(4)-TCNQ-decorated sandwiched ReS_(2)device demonstrates the formation of a vertical p-n junction in a thicker ReS_(2)device.The responsivity is as high as 2,000 A/W owing to the strong carrier separation of the p-n junction.Different thicknesses of ReS_(2)enable switching of the prominent operating mechanism between transforming deep trap states into recombination centers and forming a vertical p-n junction.The thicknessdependent doping effect of a two-dimensional material serves as a new mechanism and provides a scheme toward improving the performance of other semiconductor devices,especially optical and electronic devices based on low-dimensional materials.
基金supported by the Natural Science Foundation of Zhejiang Province(LY22E020006).
文摘Dielectric capacitors with high capacitive energy storage are urgently needed to meet the growing demand for high-performance energy storage devices.Herein,a novel lead-free Sr_(5)BiTi_(3)Nb_(7)O_(30)(SBTN)tungsten bronze relaxor ferroelectric ceramic is prepared and explored for potential energy storage applications.A high recoverable energy density Wrec(~3.72 J/cm^(3))and ultrahigh efficiencyη(~94.2%)at 380 kV/cm are achieved simultaneously.Both Wrec andηexhibit superior stabilities against temperature(30-140°C),cycles(100-105)and frequency(1-500 Hz).In addition,a high current density of 796 A/cm^(2) and a large power density of 71.7 MW/cm^(3) are achieved,together with good thermal endurance and fatigue resistance.These results demonstrate that the obtained SBTN ceramic can be deemed as the promising candidates for dielectric capacitor applications.
基金Supported by the National Natural Science Foundation of China(No.60736043)
文摘Video adaptation is a promising technique to bridge the gap between network status, device capabilities, and user preferences in pervasive media applications. However, conventional adaptation frameworks based on either transcoding or multiple pre-transcoding are not able to accommodate large numbers of users with diversified applications. This paper introduces an intermediate video description called ＂Inter- media＂, which consists of multiple level video signal components, such as texture, motion, and rate control information, as well as some semantic features, such as structural characteristics and Region Of Interest （ROI） information. It is generated off-line and stored in the video server or media gateway. Intermedia is then used to design a novel video adaptation system. The proposed adaptation system quickly and easily generates the required bit stream from Intermedia with very low complexity to fulfill a series of specific adaptation requirements, e.g., bitrate conversion, temporal/spatial resolution reduction, video summarization, ROI browsing, and some multi-level adaptations involving both signal level and semantic level adaptation. The satisfactory performance of such a system demonstrates the effectiveness and efficiency of the proposed video adaptation framework.
文摘This paper suggests the method for MPEG 2 Transport Stream ( TS ) processing and transmitting over CATV (HFC ). An MPEG 2 TS Generator Card design is presented. The system configuration and the functions of the Generator Card are given. The design of hardware and software for the card and some issues are discussed. A practical system of the application of the MPEG 2 TS Generator Card is given. A satisfactory result has been achieved in the application.
基金supported by the Hi-Tech Research and Development Program of China (2006AA01Z226)the Natural Science Foundation of Hubei, China (2007ABD002).
文摘This article proposes a mechanism of low overhead and less runtime, termed dynamic cache resources allocation （DCRA）, which allocates each application with required cache resources. The mechanism collects cache hit-miss information at runtime and then analyzes the information and decides how many cache resources should be allocated to the current executing application. The amount of cache resources varies dynamically to reduce the total number of misses and energy consumption. The study of several applications from SPEC2000 shows that significant energy saving is achieved for the application based on the DCRA with an average of 39% savings.
