共查询到20条相似文献,搜索用时 15 毫秒
1.
HU Li-jun ZHUANG Hui-zhao XUE Cheng-shan XUE Shou-bin 《半导体光子学与技术》2007,47(1):48-52
Large quantities of gallium nitride(GaN) nanowires have been prepared via ammoniating the Ga2O3 films deposited on the oxidized aluminum layer at 950℃ in a quartz tube. The nanowires have been confirmed as crystalline wurtzite GaN by X-ray diffraction, X-ray photoelectron spectrometry scanning electron microscope and selected-area electron diffraction. Transmission electron microscope (TEM) and scanning electron microscopy(SEM) reveal that the nanowires are amorphous and irregular, with diameters ranging from 30 nm to 80 nm and lengths up to tens of microns. Selected-area electron diffraction indicates that the nanowire with the hexagonal wurtzite structure is the single crystalline. The growth mechanism is discussed briefly. 相似文献
2.
ZHUANG Hui-zhao LI Bao-li XUE Cheng-shan ZHANG Shi-ying WANG De-xiao SHEN Jia-bing 《半导体光子学与技术》2008,14(1):42-47
Large-scale GaN nanowires are successfully synthesized by ammoniating Ga2O3 films on Nb layer deposited on Si(111) substrates at 850 ℃. X-ray diffraction (XRD), scanning electron microscopy (SEM), field-emssion transmission electron microscope(FETEM), Fourier transformed infrared spectrum(FTIR) are used to characterize the structural and morphological properties of the as-synthesized GaN nanowires. The results reveal that the nanowires are pure hexagonal GaN wurtzite structure with a length of about several microns and a diameter between 50 nm and 100 nm. Finally, discussed briefly is the formation mechanism of gallium nitride nanowires. 相似文献
3.
The effects of F-doping concentration on geometric structure, electronic structure and optical property of β-Ga2O3 were investigated. All F-doped β-Ga2O3 with different concentrations are easy to be formed under Ga-rich conditions, the stability and lattice parameters increase with the F-doping concentration. F-doped β-Ga2O3 materials display characteristics of the n-type semiconductor, occupied states contributed from Ga 4s, Ga 4p and O 2p states in the conduction band increase with an increase in F-doping concentration. The increase of F concentration leads to the narrowing of the band gap and the broadening of the occupied states. F-doped β-Ga2O3 exhibits the sharp band edge absorption and a broad absorption band. Absorption edges are blue-shifted, and the intensity of broad band absorption has been enhanced with respect to the fluorine content. The broad band absorption is ascribed to the intra-band transitions from occupied states to empty states in the conduction band. 相似文献
4.
Gallium oxide(Ga2O3) thin films were prepared on Si substrate by magnetron sputtering. The obtained samples were comprehensively characterized by X-ray photoelectron spectroscopy(XPS) and scanning electron microscope(SEM). Ti, Pt, Ni and AZO were deposited on the Ga2O3 thin films as electrodes. This paper mainly studies the metal-semiconductor contact formed by these four materials on the films and the influence of annealing at 500℃ on the metal-semiconductor contact. The I-V characteristics show a good linear relationship, which indicates ohmic contact between Ga2O3 and other electrodes. 相似文献
5.
Yuanqi Huang Zhengwei Chen Xiao Zhang Xiaolong Wang Yusong Zhi Zhenping Wu Weihua Tang 《半导体学报》2018,39(5):16-20
High quality epitaxial single phase (Ga0.96Mn0.04)2O3 and Ga2O3 thin films have been prepared on sapphire substrates by using laser molecular beam epitaxy (L-MBE).X-ray diffraction results indicate that the thin films have the monoclinic structure with a (-201) preferable orientation.Room temperature (RT) ferromagnetism appears and the magnetic properties of β-(Ga0.96Mn0.04)2O3 thin film are enhanced compared with our previous works.Experiments as well as the first principle method are used to explain the role of Mn dopant on the structure and magnetic properties of the thin films.The ferromagnetic properties are explained based on the concentration of transition element and the defects in the thin films. 相似文献
6.
A series of Tb^3+ doped Na Y(Mo O4)2 are synthesized by a solid-state reaction at 550 °C for 4 h, and their luminescent properties are investigated. The phase formation is carried out with X-ray powder diffraction analysis, and there is no other crystalline phase except Na Y(Mo O4)2. Na Y(Mo O4)2:Tb^3+ can produce the green emission under 290 nm radiation excitation, and the luminescence emission peak at 545 nm corresponds to the 5D4→7F5 transition of Tb^3+. The emission intensity of Tb^3+ in Na Y(Mo O4)2 is enhanced with the increase of Tb^3+ concentration, and there is no concentration quenching effect. The phenomena are proved by the decay curves of Tb^3+. Moreover, the Commission International de I'Eclairage(CIE) chromaticity coordinates of Na Y(Mo O4)2:Tb^3+ locate in the green region. 相似文献
7.
Chalcopyrite-type CulnSe2 nanoparticles are successfully prepared by using In2Se3 nanoparticles as a precursor reacted with copper chloride (CuCl) solution via a phase transformation process in low temperature. The reaction time is a key parameter. After the reaction time increasing from 0.5 h to 8 h, In2Se3 and CuCl react with each other gradually via phase transformation into CuInSe2 without any intermediate phase. The crystalline structure and morphology of the CuInSe2 nanoparticles are characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The diameter of CuInSe2 nanoparticles with good dispersibility ranges from 10 nm to 20 nm. The band gap of the CulnSe2 nanoparticles is 1.04 eV calculated from the ultraviolet-visible (UV-VIS) spectrum. 相似文献
8.
This paper provides the fabrication of Cd-free Cu(In,Ga)Se2 (CIGS) solar cells on soda-lime glass substrates. A high quality ZnS buffer layer is grown by chemical bath deposition (CBD) process with ZnSO4-NH3-SC (NH2)2 aqueous solution system. The X-ray diffraction (XRD) result shows that the as-deposited ZnS film has cubic (111) and (220) diffraction peaks. Scanning electron microscope (SEM) images indicate that the ZnS film has a dense and compact surface with good crystalline quality. Transmission measurement shows that the optical transmittance is about 90% when the wavelength is beyond 500 nm. The bandgap (Eg) value of the as-deposited ZnS film is estimated to be 3.54 eV. Finally, a competitive efficiency of 11.06% is demonstrated for the Cd-free CIGS solar cells with ZnS buffer layer after light soaking. 相似文献
9.
Lithium lutetium fluoride (LiLuF4) single crystals doped with different Dy3+ ion concentrations were grown by Bridgman method. The Judd-Ofelt (J-O) strength parameters (Ω2, Ω4, Ω6) of Dy3+ in LiLuF4 crystal are calculated according to the measured absorption spectra and the J-O theory, by which the asymmetry of the Dy3+:LiLuF4 single crystal and the possibility of attaining stimulated emission from 4F9/2 level are analyzed. The capability of the Dy3+:LiLuF4 crystal in generating white light by simultaneous blue and yellow emissions under excitation with ultra- violet light is produced. The effects of excitation wavelength and doping concentration on chromaticity coordinates and photoluminescence intensity are also investigated. Favorable CIE coordinates, x=0.319 3 and y=0.349 3, can be obtained for Dy3+ ion in 2.701% molar doping concentration under excitation of 350 nm. 相似文献
10.
A stack of Al2O3/SiNx dual layer was applied for the back side surface passivation of p-type multi-crystalline silicon solar cells, with laser-opened line metal contacts, forming a local aluminum back surface field (local Al-BSF) structure. A slight amount of Al2O3, wrapping around to the front side of the wafer during the thermal atomic layer deposition process, was found to have a negative influence on cell performance. The different process flow was found to lead to a different cell performance, because of the Al2O3 wrapping around the front surface. The best cell performance, with an absolute efficiency gain of about 0.6% compared with the normal full Al-BSF structure solar cell, was achieved when the Al2O3 layer was deposited after the front surface of the wafer had been covered by a SiNx layer. We discuss the possible reasons for this phenomenon, and propose three explanations as the Ag paste, being hindered from firing through the front passivation layer, degraded the SiNx passivation effect and the Al2O3 induced an inversion effect on the front surface. Characterization methods like internal quantum efficiency and contact resistance scanning were used to assist our understanding of the underlying mechanisms. 相似文献
11.
In Al N/Ga N heterostructures were grown on sapphire substrates by low-pressure metal organic chemical vapor deposition.The influences of NH3 flux and growth temperature on the In composition and morphologies of the In Al N were investigated by X-ray diffraction and atomic force microscopy.It’s found that the In composition increases quickly with NH3 flux decrease.But it’s not sensitive to NH3 flux under higher flux.This suggests that lower NH3 flux induces a higher growth rate and an enhanced In incorporation.The In composition also increases with the growth temperatures decreasing,and the defects of the In Al N have close relation with In composition.Unstrained In Al N with In composition of 17% is obtained at NH3 flux of 500 sccm and growth temperature of790 °C.The In Al N/Ga N heterostructure high electron mobility transistor sample showed a high two-dimensional electron gas(2DEG) mobility of 1210 cm2/(V s) with the sheet density of 2.31013cm2 at room temperature. 相似文献
12.
Whispering gallery mode (WGM)-enhanced nonlinear optical phenomena from crown-like nanostructure zinc oxide (ZnO) samples are observed. The samples are synthesized by vapor-phase transport method. The morphology and crystal struc- ture are examined and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM), and they are excited by femtosecond laser pulses with cen- tral wavelengths of 355 nm, 800 nm and 1150 nm, respectively. The typical stimulated emission presents a red shift com- pared with spontaneous emission, which is observed under the excitation of 355 nm with a relatively low threshold. The ultraviolet (UV) frequency up-conversion emission is obtained when the excitation pulse wavelengths are selected as 800 nm and 1150 nm, respectively. The peak position and the relationship between the emission intensity and excitation inten- sity demonstrate that the UV up-conversion photoluminescence (PL) is induced by two- and three-photon absorptions. The PL characteristics and their WGM-enhanced mechanism are investigated. 相似文献
13.
A novel In Ga N back barrier high electron mobility transistors structure with a compositionally stepgraded Al Ga N barrier layer was grown by metal organic chemical vapor deposition on sapphire substrate.The structural and electrical properties of two samples were investigated and compared:the first sample is the stepgraded structure and the second one is the high Al structure as a comparison.By calculating full width at half maximum of XRD measurements,the densities of screw-type threading dislocations are 8.34108cm2and11.44108cm2 for step-graded structure and high Al structure,respectively,which are consistent with the results of atomic force microscopy.By Hall measurements,the measured two-dimensional electron gas mobility was 1820 cm2/(V s) for step-graded structure,and 1300 cm2/(V s) for high Al structure,respectively.The stepgraded structure improves the crystal quality of Al Ga N layer due to the released lattice strain.The device was fabricated and leakage current is only 28 A when the drain voltage is 10 V; it was found that the In Ga N back barrier could effectively reduce the buffer leakage current. 相似文献
14.
Shengnan Zhang Xiaozheng Lian Yanchao Ma Weidan Liu Yingwu Zhang Yongkuan Xu Hongjuan Cheng 《半导体学报》2018,39(8):27-31
β-Ga2O3 is an ultra-wide band-gap semiconductor with promising applications in UV optical detectors,Schottky barrier diodes,field-effect transistors and substrates for light-emitting diodes.However,the preparation of large β-Ga2O3 crystals is undeveloped and many properties of this material have not been discovered yet.In this work,2-inch β-Ga2O3 single crystals were grown by using an edge-defined film-fed growth method.The high quality of the crystal has been proved by high-resolution X-ray diffraction with 19.06 arcsec of the full width at half maximum.The electrical properties and optical properties of both the unintentionally doped and Si-doped β-Ga2O3 crystals were investigated systematically. 相似文献
15.
The xonotlite fibers were synthesized via the hydrothermal synthesis method with CaO and SiO2 as the raw materials and the molar ratio of Si/Ca of 1.0. Effect of anions from various calcium sources on the microstructure of the xonotlite fibers is studied in this paper. These obtained products were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM) techniques to investigate their crystalline phase, crystal structure and morphology. The results indicate that anion from various calcium sources has little influence on the crystalline phases of xonotlite fibers but poses a great impact on their morphologies. Xonotlite fibers with single crystal characteristics and large aspect ratio of 50—100 were successfully fabricated from CaCl2 as calcium material at 225 °C for 15 h. The existence of Cl? anion in the CaO-SiO2-H2O system significantly contributes to the formation of xonotlite crystal. 相似文献
16.
Cu and Cu/ITO films were prepared on polyethylene terephthalate (PET) substrates with a Ga2O3 buffer layer using radio frequency (RF) and direct current (DC) magnetron sputtering. The effect of Cu layer thickness on the optical and electrical properties of the Cu film deposited on a PET substrate with a Ga2O3 buffer layer was studied, and an appropriate Cu layer thickness of 4.2 nm was obtained. Changes in the optoelectrical properties of Cu(4.2 nm)/ITO(30 nm) films were investigated with respect to the Ga2O3 buffer layer thickness. The optical and electrical properties of the Cu/ITO films were significantly influenced by the thickness of the Ga2O3 buffer layer. A maximum transmission of 86%, sheet resistance of 45 Ω/□ and figure of merit of 3.96 × 10^-3 Ω^ -1 were achieved for Cu(4.2 nm)/ITO(30 nm) films with a Ga2O3 layer thickness of 15 nm. 相似文献
17.
In order to obtain higher emission performance than that of a traditional M-type cathode, we have developed a new type impregnated dispenser cathode. The new cathode is impregnated with a new active substance with molar ratio of 26BaO·29SrO·8Sc2O3 ·7CaO·Al2O3 . This paper introduces the emission performance, surface active material, and work function of the new cathode. At 1100℃B , the DC current density and pulse current density are 30.6±1.0 A/cm2 and 171.6±2.8 A/cm2 , respectively, 2.1 and 5.4 times of that of an M-type cathode. The work function of the new cathode is 1.668± 0.002 eV. High concentration O-Al-Sc-Sr-Ba and O-Al-Sc-Ba are found in the pores and at pore edges, respectively. By comparing the emission performances and surface characteristics of as-polished and as-cleaned cathodes, it is proposed that, the emission around pore ends forms the major part of the total emission for the new cathodes. 相似文献
18.
IrlAs0.6P0.4 epilayers grown by low-pressure metal organic chemical vapor deposition (LP-MOCVD) on InP (100) sub- strate are investigated. The influence of growth temperature on crystalline quality of InAs0.6P0.4 epilayer is character- ized by scanning electron microscopy (SEM), Hall measurements, photoluminescence (PL) spectra, and the Raman properties are analyzed by Raman scattering spectrum. The characterization results show that the crystalline quality and Raman property of InAs0.6P0.4 epilayers have close relation to the growth temperature. It indicates that 530 ℃ is the optimum growth temperature to get good quality and properties of InAs0.6P0.4 epilayers. 相似文献
19.
LIMeng-chao FUXing WEIXiao-lei HUXiao-tang 《半导体光子学与技术》2003,9(4):230-233
The influence of vibration is already one of main obstacles for improving the nano measuring accuracy. The techniques of anti--vibration,vibration isolation and vibration compensation become an important branch in nano measuring field. Starting with the research of sensitivity to vibration of scanning tunneling microscope(STM), the theory, techniques and realization methods of nano vibration sensor based on tunnel effect are initially investigated, followed by developing the experimental devices. The experiments of the vibration detection and vibration compensation are carried out. The experimental results show that vibration sensor based on tunnel effect is characterized by high sensitivity, good frequency characteristic and the same vibratory response characteristic consistent with STM. 相似文献
20.
The Hamiltonian of a quantum rod with an ellipsoidal boundary is given after a coordinate transformation which changes the ellipsoidal boundary into a spherical one. We then study the first internal excited state energy, the excitation energy and the frequency of the transition spectral line between the first internal excited state and the ground state of the strong-coupling polaron in a quantum rod. The effects of the electron–phonon coupling strength, the aspect ratio of the ellipsoid, the transverse radius of quantum rods and the transverse and longitudinal effective confinement length are taken into consideration by using a linear combination operator and the unitary transformation methods. It is found that the first internal excited state energy, the excitation energy and the frequency of the transition spectral line are increasing functions of the electron–phonon coupling strength, whereas they are decreasing ones of the transverse radius of quantum rods and the aspect ratio. The first internal excited state energy, the excitation energy and the frequency of the transition spectral line increase with decreasing transverse and longitudinal effective confinement length. oindent 相似文献