The study of oxide heteroepitaxy has been hindered by the issues of misfit strain and substrate clamping,which impede both the optimization of performance and the acquisition of a fundamental understanding of oxide sy...The study of oxide heteroepitaxy has been hindered by the issues of misfit strain and substrate clamping,which impede both the optimization of performance and the acquisition of a fundamental understanding of oxide systems.Recently,however,the development of freestanding oxide membranes has provided a plausible solution to these substrate limitations.Single-crystalline functional oxide films can be released from their substrates without incurring significant damage and can subsequently be transferred to any substrate of choice.This paper discusses recent advancements in the fabrication,adjustable physical properties,and various applications of freestanding oxide perovskite films.First,we present the primary strategies employed for the synthesis and transfer of these freestanding perovskite thin films.Second,we explore the main functionalities observed in freestanding perovskite oxide thin films,with special attention to the tunable functionalities and physical properties of these freestanding perovskite membranes under varying strain states.Next,we encapsulate three representative devices based on freestanding oxide films.Overall,this review highlights the potential of freestanding oxide films for the study of novel functionalities and flexible electronics.展开更多
A differential equation that is generally effective for squeeze film air damping of perforated plate and non perforated plate as well as in MEMS devices is developed.For perforated plate,the thickness and the dimens...A differential equation that is generally effective for squeeze film air damping of perforated plate and non perforated plate as well as in MEMS devices is developed.For perforated plate,the thickness and the dimensions of the plate are not limited.With boundary conditions,pressure distribution and the damping force on the plate can be found by solving the differential equation.Analytical expressions for damping pressure and damping force of a long strip holeplate are presented with a finite thickness and a finite width.To the extreme conditions of very thin plate and very thin hole,the results are reduced to the corresponding results of the conventional Reynolds' equation.Thus, the effectiveness of the generalized differential equation is justified.Therefore,the generalized Reynolds' equation will be a useful tool of design for damping structures in MEMS.展开更多
Based on the first-principles computational method and the elastic scattering Green＇s function theory, we have investigated the electronic transport properties of different oligothiophene molecular junctions theoreti...Based on the first-principles computational method and the elastic scattering Green＇s function theory, we have investigated the electronic transport properties of different oligothiophene molecular junctions theoretically. The numerical results show that the difference of geometric symmetries of the oligothiophene molecules leads to the difference of the contact configurations between the molecule and the electrodes, which results in the difference of the coupling parameters between the molecules and electrodes as well as the delocalization properties of the molecular orbitals. Hence, the series of oligothiophene molecular junctions display unusual conductive properties on the length dependence.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
The influence of DBR in resonant cavity on the characteristics of the reflectivity of InGaAs/GaAs MQW SEED arrays has been discussed. InGaAs/GaAs acting as the active region of MQW SEED to gain 980nm work wavele...The influence of DBR in resonant cavity on the characteristics of the reflectivity of InGaAs/GaAs MQW SEED arrays has been discussed. InGaAs/GaAs acting as the active region of MQW SEED to gain 980nm work wavelergth has been introduced. A new resonant cavity structure of the InGaAs/GaAs MQW SEED arrays has been designed and analyzed. The MQW materials grown by MOCVD system have also been measured and analyzed with micro optical spot reflection spectra, PL measurement and X ray measurement. The results of measurement prove the good quality of the wafer and the accuracy of our design and analysis of the structure of the device.展开更多
AlGaN/AlN/GaN high electron mobility transistor （HEMT） structures with a high-mobility GaN thin layer as a channel are grown on high resistive 6H-SiC substrates by metalorganic chemical vapor deposition. The HEMT st...AlGaN/AlN/GaN high electron mobility transistor （HEMT） structures with a high-mobility GaN thin layer as a channel are grown on high resistive 6H-SiC substrates by metalorganic chemical vapor deposition. The HEMT structure exhibits a typical two-dimensional electron gas （2DEG） mobility of 1944cm^2/（V·s） at room temperature and 11588cm^2/（V ·s） at 80K with almost equal 2DEG concentrations of about 1.03 × 10^13 cm^-2. High crystal quality of the HEMT structures is confirmed by triple-crystal X-ray diffraction analysis. Atomic force microscopy measurements reveal a smooth AlGaN surface with a root-mean-square roughness of 0.27nm for a scan area of 10μm × 10μm. HEMT devices with 0.8μm gate length and 1.2mm gate width are fabricated using the structures. A maximum drain current density of 957mA/mm and an extrinsic transconductance of 267mS/mm are obtained.展开更多
A Si doped AlGaN/GaN HEMT structure with high Al content (x=43%) in the barrier layer is grown on sapphire substrate by RF-MBE.The structural and electrical properties of the heterostructure are investigated by the tr...A Si doped AlGaN/GaN HEMT structure with high Al content (x=43%) in the barrier layer is grown on sapphire substrate by RF-MBE.The structural and electrical properties of the heterostructure are investigated by the triple axis X-ray diffraction and Van der Pauw-Hall measurement,respectively.The observed prominent Bragg peaks of the GaN and AlGaN and the Hall results show that the structure is of high quality with smooth interface.The high 2DEG mobility in excess of 1260cm2/(V·s) is achieved with an electron density of 1.429×10 13cm -2 at 297K,corresponding to a sheet-density-mobility product of 1.8×10 16V -1·s -1.Devices based on the structure are fabricated and characterized.Better DC characteristics,maximum drain current of 1.0A/mm and extrinsic transconductance of 218mS/mm are obtained when compared with HEMTs fabricated using structures with lower Al mole fraction in the AlGaN barrier layer.The results suggest that the high Al content in the AlGaN barrier layer is promising in improving material electrical properties and device performance.展开更多
Both the vertical cavity surface emitting diodes and detectors are fabricated by using the epitaxial wafer with resonant cavity structure.Their characteristics are analyzed.The light emitters have high spectral purity...Both the vertical cavity surface emitting diodes and detectors are fabricated by using the epitaxial wafer with resonant cavity structure.Their characteristics are analyzed.The light emitters have high spectral purity of 4 8nm and high electroluminescence intensity of 0 7mW while injection current is 50mA.A 1×16 array of surface emitting light device is tested on line by probes and then used for module.The light detectors have wavelength selectivity and space selectivity.The required difference in input mirror reflectivity between emitters and detectors can easily be achieved though varying the numbers of top DBR period by etching.展开更多
The effect of HALO dose on device parameter degradation of pMOSFET with 2.1nm o xide and 0.135μm channel length at hot carrier stress is analyzed.It is found that the degradation mechanism is not sensitive to HALO d...The effect of HALO dose on device parameter degradation of pMOSFET with 2.1nm o xide and 0.135μm channel length at hot carrier stress is analyzed.It is found that the degradation mechanism is not sensitive to HALO dose changing,but the d egradation quantities of linear drain current,saturation drain current,and maxim um transconductance increase with HALO dose enhancing and are larger than those of speculated before.The degradation of device parameters (linear drain current, saturation drain current,and maximum transconductance) is attributed to not onl y the drain series resistance enhancing induced by interface states under spacer oxide and carrier mobility degradation but also the threshold voltage variation and initial threshold voltage increasing with HALO dose enhancing.展开更多
The growth, fabrication, and characterization of 0. 2μm gate-length AlGaN/GaN HEMTs, with a high mobility GaN thin layer as a channel,grown on （0001） sapphire substrates by MOCVD,are described. The unintentionally ...The growth, fabrication, and characterization of 0. 2μm gate-length AlGaN/GaN HEMTs, with a high mobility GaN thin layer as a channel,grown on （0001） sapphire substrates by MOCVD,are described. The unintentionally doped 2.5μm thick GaN epilayers grown with the same conditions as the GaN channel have a room temperature electron mobility of 741cmz^2（V· s） at an electron concentration of 1.52 × 10^16 cm^-3. The resistivity of the thick GaN buffer layer is greater than 10^8Ω· cm at room temperature. The 50mm HEMT wafers grown on sapphire substrates show an average sheet resistance of 440.9Ω□ with uniformity better than 96%. Devices of 0.2μm× 40μm gate periphery exhibit a maximum extrinsic transconductance of 250mS/mm and a current gain cutoff frequency of 77GHz. The AlGaN/GaN HEMTs with 0.8mm gate width display a total output power of 1.78W （2.23W/mm） and a linear gain of 13.3dB at 8GHz. The power devices also show a saturated current density as high as 1.07A/mm at a gate bias of 0.5V.展开更多
A diamond-like carbon （DLC） film is deposited as an electron injection layer between the polymer light-emitting layer（MEH-PPV） and aluminum （Al） cathode electrode in polymer electroluminescence devices （PLEDs）...A diamond-like carbon （DLC） film is deposited as an electron injection layer between the polymer light-emitting layer（MEH-PPV） and aluminum （Al） cathode electrode in polymer electroluminescence devices （PLEDs） using a radio frequency plasma deposition system. The source material of the DLC is n-butylamine. The devices consist of indium tin oxide （ITO）/MEH-PPV/DLC/Al. Electron injection properties are investigated through I-V characteristics,and the mechanism of electron injection enhancement due to a thin DLC layer has been studied. It is found that： （1） a DLC layer thinner than 1.0nm leads to a higher turn-on voltage and decreased electroluminescent （EL） efficiency; （2） a 5.0nm DLC layer significantly enhances the electron injection and results in the lowest turn-on voltage and the highest EL efficiency; （3） DLC layer that exceeds 5.0nm results in poor device performance;and（4） EL emission can hardly be detected when the layer exceeds 10.0nm. The properties of ITO/MEH-PPV/DLC/Al and ITO/MEH-PPV/LiF/Al are investigated comparatively.展开更多
基金supported by the Fundamental Research Funds for the Central Universities(WK9990000102,WK2030000035).
文摘The study of oxide heteroepitaxy has been hindered by the issues of misfit strain and substrate clamping,which impede both the optimization of performance and the acquisition of a fundamental understanding of oxide systems.Recently,however,the development of freestanding oxide membranes has provided a plausible solution to these substrate limitations.Single-crystalline functional oxide films can be released from their substrates without incurring significant damage and can subsequently be transferred to any substrate of choice.This paper discusses recent advancements in the fabrication,adjustable physical properties,and various applications of freestanding oxide perovskite films.First,we present the primary strategies employed for the synthesis and transfer of these freestanding perovskite thin films.Second,we explore the main functionalities observed in freestanding perovskite oxide thin films,with special attention to the tunable functionalities and physical properties of these freestanding perovskite membranes under varying strain states.Next,we encapsulate three representative devices based on freestanding oxide films.Overall,this review highlights the potential of freestanding oxide films for the study of novel functionalities and flexible electronics.
文摘A differential equation that is generally effective for squeeze film air damping of perforated plate and non perforated plate as well as in MEMS devices is developed.For perforated plate,the thickness and the dimensions of the plate are not limited.With boundary conditions,pressure distribution and the damping force on the plate can be found by solving the differential equation.Analytical expressions for damping pressure and damping force of a long strip holeplate are presented with a finite thickness and a finite width.To the extreme conditions of very thin plate and very thin hole,the results are reduced to the corresponding results of the conventional Reynolds' equation.Thus, the effectiveness of the generalized differential equation is justified.Therefore,the generalized Reynolds' equation will be a useful tool of design for damping structures in MEMS.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.10804064 and No.10974121）. The author would like to thank professor Chuan-Kui Wang for his helpful discussions.
文摘Based on the first-principles computational method and the elastic scattering Green＇s function theory, we have investigated the electronic transport properties of different oligothiophene molecular junctions theoretically. The numerical results show that the difference of geometric symmetries of the oligothiophene molecules leads to the difference of the contact configurations between the molecule and the electrodes, which results in the difference of the coupling parameters between the molecules and electrodes as well as the delocalization properties of the molecular orbitals. Hence, the series of oligothiophene molecular junctions display unusual conductive properties on the length dependence.
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The influence of DBR in resonant cavity on the characteristics of the reflectivity of InGaAs/GaAs MQW SEED arrays has been discussed. InGaAs/GaAs acting as the active region of MQW SEED to gain 980nm work wavelergth has been introduced. A new resonant cavity structure of the InGaAs/GaAs MQW SEED arrays has been designed and analyzed. The MQW materials grown by MOCVD system have also been measured and analyzed with micro optical spot reflection spectra, PL measurement and X ray measurement. The results of measurement prove the good quality of the wafer and the accuracy of our design and analysis of the structure of the device.
文摘AlGaN/AlN/GaN high electron mobility transistor （HEMT） structures with a high-mobility GaN thin layer as a channel are grown on high resistive 6H-SiC substrates by metalorganic chemical vapor deposition. The HEMT structure exhibits a typical two-dimensional electron gas （2DEG） mobility of 1944cm^2/（V·s） at room temperature and 11588cm^2/（V ·s） at 80K with almost equal 2DEG concentrations of about 1.03 × 10^13 cm^-2. High crystal quality of the HEMT structures is confirmed by triple-crystal X-ray diffraction analysis. Atomic force microscopy measurements reveal a smooth AlGaN surface with a root-mean-square roughness of 0.27nm for a scan area of 10μm × 10μm. HEMT devices with 0.8μm gate length and 1.2mm gate width are fabricated using the structures. A maximum drain current density of 957mA/mm and an extrinsic transconductance of 267mS/mm are obtained.
文摘A Si doped AlGaN/GaN HEMT structure with high Al content (x=43%) in the barrier layer is grown on sapphire substrate by RF-MBE.The structural and electrical properties of the heterostructure are investigated by the triple axis X-ray diffraction and Van der Pauw-Hall measurement,respectively.The observed prominent Bragg peaks of the GaN and AlGaN and the Hall results show that the structure is of high quality with smooth interface.The high 2DEG mobility in excess of 1260cm2/(V·s) is achieved with an electron density of 1.429×10 13cm -2 at 297K,corresponding to a sheet-density-mobility product of 1.8×10 16V -1·s -1.Devices based on the structure are fabricated and characterized.Better DC characteristics,maximum drain current of 1.0A/mm and extrinsic transconductance of 218mS/mm are obtained when compared with HEMTs fabricated using structures with lower Al mole fraction in the AlGaN barrier layer.The results suggest that the high Al content in the AlGaN barrier layer is promising in improving material electrical properties and device performance.
文摘Both the vertical cavity surface emitting diodes and detectors are fabricated by using the epitaxial wafer with resonant cavity structure.Their characteristics are analyzed.The light emitters have high spectral purity of 4 8nm and high electroluminescence intensity of 0 7mW while injection current is 50mA.A 1×16 array of surface emitting light device is tested on line by probes and then used for module.The light detectors have wavelength selectivity and space selectivity.The required difference in input mirror reflectivity between emitters and detectors can easily be achieved though varying the numbers of top DBR period by etching.
文摘The effect of HALO dose on device parameter degradation of pMOSFET with 2.1nm o xide and 0.135μm channel length at hot carrier stress is analyzed.It is found that the degradation mechanism is not sensitive to HALO dose changing,but the d egradation quantities of linear drain current,saturation drain current,and maxim um transconductance increase with HALO dose enhancing and are larger than those of speculated before.The degradation of device parameters (linear drain current, saturation drain current,and maximum transconductance) is attributed to not onl y the drain series resistance enhancing induced by interface states under spacer oxide and carrier mobility degradation but also the threshold voltage variation and initial threshold voltage increasing with HALO dose enhancing.
文摘The growth, fabrication, and characterization of 0. 2μm gate-length AlGaN/GaN HEMTs, with a high mobility GaN thin layer as a channel,grown on （0001） sapphire substrates by MOCVD,are described. The unintentionally doped 2.5μm thick GaN epilayers grown with the same conditions as the GaN channel have a room temperature electron mobility of 741cmz^2（V· s） at an electron concentration of 1.52 × 10^16 cm^-3. The resistivity of the thick GaN buffer layer is greater than 10^8Ω· cm at room temperature. The 50mm HEMT wafers grown on sapphire substrates show an average sheet resistance of 440.9Ω□ with uniformity better than 96%. Devices of 0.2μm× 40μm gate periphery exhibit a maximum extrinsic transconductance of 250mS/mm and a current gain cutoff frequency of 77GHz. The AlGaN/GaN HEMTs with 0.8mm gate width display a total output power of 1.78W （2.23W/mm） and a linear gain of 13.3dB at 8GHz. The power devices also show a saturated current density as high as 1.07A/mm at a gate bias of 0.5V.
文摘A diamond-like carbon （DLC） film is deposited as an electron injection layer between the polymer light-emitting layer（MEH-PPV） and aluminum （Al） cathode electrode in polymer electroluminescence devices （PLEDs） using a radio frequency plasma deposition system. The source material of the DLC is n-butylamine. The devices consist of indium tin oxide （ITO）/MEH-PPV/DLC/Al. Electron injection properties are investigated through I-V characteristics,and the mechanism of electron injection enhancement due to a thin DLC layer has been studied. It is found that： （1） a DLC layer thinner than 1.0nm leads to a higher turn-on voltage and decreased electroluminescent （EL） efficiency; （2） a 5.0nm DLC layer significantly enhances the electron injection and results in the lowest turn-on voltage and the highest EL efficiency; （3） DLC layer that exceeds 5.0nm results in poor device performance;and（4） EL emission can hardly be detected when the layer exceeds 10.0nm. The properties of ITO/MEH-PPV/DLC/Al and ITO/MEH-PPV/LiF/Al are investigated comparatively.
