全文获取类型
收费全文 | 276篇 |
免费 | 82篇 |
国内免费 | 10篇 |
专业分类
化学 | 61篇 |
晶体学 | 69篇 |
综合类 | 3篇 |
数学 | 2篇 |
物理学 | 233篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 5篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 6篇 |
2017年 | 11篇 |
2016年 | 9篇 |
2015年 | 7篇 |
2014年 | 11篇 |
2013年 | 17篇 |
2012年 | 14篇 |
2011年 | 21篇 |
2010年 | 25篇 |
2009年 | 12篇 |
2008年 | 22篇 |
2007年 | 24篇 |
2006年 | 25篇 |
2005年 | 33篇 |
2004年 | 28篇 |
2003年 | 11篇 |
2002年 | 9篇 |
2001年 | 5篇 |
2000年 | 17篇 |
1999年 | 10篇 |
1998年 | 2篇 |
1997年 | 7篇 |
1996年 | 9篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
排序方式: 共有368条查询结果,搜索用时 15 毫秒
61.
High-performance InGaN/GaN MQW LEDs with Al-doped ZnO transparent conductive layers grown by MOCVD using H_2O as an oxidizer
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In this study,the high performance of InGaN/GaN multiple quantum well light-emitting diodes(LEDs) with Aldoped ZnO(AZO) transparent conductive layers(TCLs) has been demonstrated.The AZO-TCLs were fabricated on the n~+-InGaN contact layer by metal organic chemical vapor deposition(MOCVD) using H_2O as an oxidizer at temperatures as low as 400 ℃ without any post-deposition annealing.It shows a high transparency(98%),low resistivity(510 ~4 Ω·cm),and an epitaxial-like excellent interface on p-GaN with an n+-InGaN contact layer.A forward voltage of 2.82 V @ 20 mA was obtained.Most importantly,the power efficiencies can be markedly improved by 53.8%@20 mA current injection and 39.6%@350 mA current injection compared with conventional LEDs with indium tin oxide TCL(LED-Ⅲ),and by28.8%@20 mA current injection and 4.92%@350 mA current injection compared with LEDs with AZO-TCL prepared by MOCVD using O_2 as an oxidizer(LED-Ⅱ),respectively.The results indicate that the AZO-TCL grown by MOCVD using H_2O as an oxidizer is a promising TCL for a low-cost and high-efficiency GaN-based LED application. 相似文献
62.
Haisheng Fang Zhi Zhang Yaoyu Pan Ronghui Ma Sheng Liu Mengying Wang 《Crystal Research and Technology》2014,49(11):907-918
Gallium nitride (GaN) is a direct bandgap semiconductor widely used in bright light‐emitting diodes (LEDs). Thin‐film GaN is grown by metal‐organic chemical vapour deposition (MOCVD) technique. Reliability, efficiency and durability of LEDs are influenced critically by the quality of GaN films. In this report, a systematic study has been performed to investigate and optimize the growth process. Fluid flow, heat transfer and chemical reactions are calculated for a specific close‐coupled showerhead (CCS) MOCVD reactor. Influences of reactor dimensions and growth parameters have been examined after introducing the new conceptions of growth uniformity and growth efficiency. It is found that GaN growth rate is mainly affected by the concentration of (CH3)3Ga:NH3 on the susceptor, while growth uniformity is mainly influenced by the recirculating flows above the susceptor caused by natural convection. Effect of gas inlet temperature and the susceptor temperature over the growth rate can be explained by two competing mechanisms. High growth efficiency can be achieved by optimizing the reactor design. 相似文献
63.
本实验采用普通的光刻和湿法腐蚀技术,将GaAs基片刻蚀成具有W形沟槽样的非平面结构,基片表面为(100)面,沟槽的侧斜面为(111)B面.在此基片上用低压MOCVD设备外延生长了GaAs/GaAsP多层膜,通过扫描电镜和微区拉曼光谱,研究它们的生长特性,发现GaAs和GaAsP的生长速率与基片的晶向及基片上的生长位置有关.根据这一生长特性,选择合适的W形沟道形状,用常规的量子阱外延方式,在W形沟道中央顶部突起的线条状平面上形成宝塔形生长,从而在尖端长出量子线.低温荧光光谱中观察到相应的能量峰,从而证实量子线的存在. 相似文献
64.
Jingchang Sun Qiuju Feng Jiming Bian Dongqi Yu Chengren Li Jianze Zhao Guotong Du 《Journal of luminescence》2011,131(4):825-828
A p-ZnO:N/n-GaN:Si structure heterojunction light-emitting diode (LED) is fabricated on c-plane sapphire by full metal organic chemical vapor deposition (MOCVD) technique. The p-type layer with hole concentration of 8.94×1016 cm−3 is composed of nitrogen-doped ZnO using NH3 as the doping source with subsequent annealing in N2O plasma ambient. Silicon-doped GaN film with electron concentration of 1.15×1018 cm−3 is used as the n-type layer. Desirable rectifying behavior is observed from the current-voltage (I-V) curve of the device. The forward turn on voltage is about 4 V and the reverse breakdown voltage is more than 7 V. A distinct ultraviolet (UV) electroluminescence (EL) with a dominant emission peak centered at 390 nm is detected at room temperature from the heterojunction structure under forward bias conditions. The origins of the EL emissions are discussed in comparison with the photoluminescence (PL) spectra. 相似文献
65.
《Journal of Coordination Chemistry》2012,65(2):111-117
Abstract The synthesis and structure of the indium dithiocarbamate, In[S2CN(CH3)2]3·(1/2) 4-mepy (4-mepy=4-methylpyridine), is described. Indium metal was oxidized by tetramethylthiuram disulfide in 4-methylpyridine at 25°C to form a new, homoleptic indium(III) dithiocarbamate in yields exceeding 60%. In[S2CN(CH3)2]3 exists as a discrete molecule with a distorted-octahedral geometry. The compound crystallizes in the P 1 (No. 2) space group with a=9.282(1)Å, b=10.081(1)Å, c=12.502Å, α=73.91(1)°, β=70.21(1)°, γ=85.84(1)°, Z=2, V(Å)=1057.3(3), R=0.046 and Rw =0.061. 相似文献
66.
Analysis and finite element simulation of electromagnetic heating in the nitride MOCVD reactor
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Electromagnetic field distribution in the vertical metal
organic chemical vapour deposition (MOCVD) reactor is simulated by
using the finite element method (FEM). The effects of alternating
current frequency, intensity, coil turn number and the distance
between the coil turns on the distribution of the Joule heat are
analysed separately, and their relations to the value of Joule heat
are also investigated. The temperature distribution on the
susceptor is also obtained. It is observed that the results of the
simulation are in good agreement with previous measurements. 相似文献
67.
Dependence of bimodal size distribution on temperature and optical properties of InAs quantum dots grown on vicinal GaAs (100) substrates by using MOCVD
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Self-assembled InAs quantum dots (QDs) are grown on vicinal GaAs (100)
substrates by using metal-organic chemical vapour deposition (MOCVD). An
abnormal temperature dependence of bimodal size distribution of InAs quantum
dots is found. As the temperature increases, the density of the small dots
grows larger while the density of the large dots turns smaller, which is
contrary to the evolution of QDs on exact GaAs (100) substrates. This trend
is explained by taking into account the presence of multiatomic steps on the
substrates. The optical properties of InAs QDs on vicinal GaAs(100)
substrates are also studied by photoluminescence (PL) . It is found that
dots on a vicinal substrate have a longer emission wavelength, a narrower PL
line width and a much larger PL intensity. 相似文献
68.
Homo-epitaxial GaN growth on exact and misoriented single crystals: suppression of hillock formation
A. R. A. Zauner J. L. Weyher M. Plomp V. Kirilyuk I. Grzegory W. J. P. van Enckevort J. J. Schermer P. R. Hageman P. K. Larsen 《Journal of Crystal Growth》2000,210(4):435-443
GaN single crystals were used as substrates for MOCVD growth. The (
) plane of the substrate crystals was polished to obtain off-angle orientations of 0, 2, and 4° towards the [
] direction. The highest misorientation resulted in a reduction of the hexagonal hillock density by nearly two orders of magnitude as compared with homo-epitaxial films grown on the exact (
) surface. The features that are still found on the 4° off-angle sample after growth can be explained by a model involving the interaction of steps, introduced by the misorientation, and the hexagonal hillocks during the growth process. Following from this explanation it could be concluded that surface diffusion is found to be not important during growth on the N-side. The material quality of the N-side was examined by photoluminescence (PL) measurements. The PL spectrum measured at 5 K shows dominant donor bound excitons with a FWHM of 1.4 meV as well as free excitonic transitions. 相似文献
69.
本文研究了薄膜厚度对MOCVD技术制备未掺杂ZnO薄膜的微观结构和电学特性影响.XRD和SEM的研究结果表明,随着薄膜厚度的增加,ZnO薄膜(110)峰趋于择优取向,且晶粒逐渐长大,薄膜从球状和细长棒状演变为具有类金字塔绒面结构特征的ZnO薄膜;Hall测量表明,较厚的ZnO薄膜有助于提高薄膜电学特性,可归于晶粒长大和晶体质量提高.40min沉积时间(膜厚为1250nm)制备出的ZnO薄膜具有明显绒面结构,其晶粒尺寸为300~500nm,电阻率为7.9×10-3Ω·cm,迁移率为26.8cm2/Vs. 相似文献
70.
YANGHong-jun ZHAOBai-jun FANGXiu-jun DUGuo-tong LIUDa-li GAOChun-xiao LIUXi-zhe 《高等学校化学研究》2005,21(2):137-140
Piezoelectric ZnO layers with high resistivity for surface acoustic wave applications were prepared on polycrystalline diamond/Si substrates with(Ill) orientation via metal-organic chemical vapour deposition.The characteristics of the films were optimized through different growth methods. The comparative study of the X-ray diffraction spectra and scanning electron microscopic images showed that the final-prepared ZnO films were dominantly c-axis oriented. Zn and O elements in the final prepared ZnO films were investigated through X-ray photoelectron spectroscopy. According to the statistical results, the n(Zn)/n(O) ratio is near 1. The Raman scattering was also performed in back scattering configuration. E2 mode was observed for the final films, which indicated that the better quality ZnO films had been obtained. The resistivity of the films was also enhanced via the modification of the growth methods. 相似文献