共查询到19条相似文献,搜索用时 62 毫秒
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空间电荷效应是影响束流传输和束流品质的一个重要因素,特别是对于低能量强流离子束来说。离子束与束流传输线中的剩余气体分子通过电离反应等产生大量二次电子,受离子束的空间电势约束,可以部分补偿空间电荷效应。为了深入研究强流束在低能段的传输,需要准确测量束流的空间电荷补偿度(SCCD),尤其是混合束流的SCCD。利用一台三栅网式能量分析仪和一台基于128通道皮安表系统构成的束流剖面探测器,分别测量了不同流强和束流分布下的混合O离子束的二次离子能量分布和束流流强分布,从而计算得出SCCD。实验结果表明,在1.0×10-5 Pa的真空度下,不同流强的混合O离子束的SCCD基本在70%左右;不同束流分布对空间电势分布影响较大,对离子束的SCCD也会有一定程度的影响。 相似文献
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采用背散射(RBS)/沟道(channeling)分析和傅里叶变换红外光谱(FT-IR)研究了掺铒G aN薄膜的晶体结构和光致发光(PL)特性.背散射/沟道分析结果表明:随退火温度的升高, 薄膜中辐照损伤减少;但当退火温度达到1000℃,薄膜中的缺陷又明显增加.Er浓度随注入 深度呈现高斯分布.通过沿GaN的<0001>轴方向的沟道分析,对于900℃,30min退火的GaN:Er 样品,Er在晶格中的替位率约76%.光谱研究表明:随退火温度的升高,室温下样品的红外P L峰强度增加;但是当退火温度达到100
关键词:
GaN
Er
离子束分析
光致发光 相似文献
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提高离子束刻蚀亚微米光栅侧壁陡直度的方法 总被引:2,自引:1,他引:1
现代亚微米光栅的应用通常要求栅脊侧壁陡直。通过比较两种配备不同离子源的刻蚀机的反应离子束刻蚀结果,认为影响亚微米光栅侧壁陡直度的一个重要因素是离子束发散角(束散角),且小束散角有利于获得陡直的光栅侧壁。国内应用最广泛的双栅考夫曼刻蚀机束散角较大(大于13°),致使用常规方法获得的熔石英光栅的侧壁倾角仅为77°。针对此刻蚀机,尝试了三种提高侧壁陡直度的方法:旋转倾斜刻蚀法、交替倾斜刻蚀法和二次金属掩模法,分别把侧壁倾角提高到86°、86°和82°。最后从掩模侧壁收缩速率和槽底部与顶部离子通量的差异对束散角对侧壁陡直度的影响给予解释,并说明了上述三种方法的工作机理。 相似文献
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对于低能强流离子束来说,空间电荷效应的存在将导致束流发散、发射度增加等一系列问题,从而降低束流品质。幸运的是,当束流由离子源引出通过低能传输线时会与其中的剩余气体发生电离反应,产生二次电子与二次离子;二次电子在束流自身产生的电场作用下,在束流中积累并中和部分空间电荷,达到抑制空间电荷效应的效果。为了测量空间电荷中和程度,中国科学院近代物理研究所研制了一台三栅网式能量分析仪用以测量电离过程中产生的二次离子能量来间接计算空间电荷中和度。实验结果表明,对于40 keV, 18.5 mA的质子束,真空度为1.510*3 Pa 时得到最佳补偿度;真空度一定的情况下,空间电荷补偿度随束流流强增加而变大。For high-intensity low-energy ion beams, space charge effect is a main cause of beam divergence and emittance growth. Fortunately, residual gas molecules in the drift space tend to be ionized and neutralize the beam space charge spontaneously. The level of Space Charge Neutralization (SCN)is measured through the detection of created secondary ion energy distribution in the beam region. A so-called non-interceptive Three-grid Energy Analyzer (TEA) has been designed and manufactured at Institute of Modern Physics, Chinese Academy of Sciences (IMP). This paper will present the detailsof the TEA detector and the application to diagnose proton beam SCN level in the Low Energy Beam Transport (LEBT) line. As a preliminary result, for an 18.5 mA proton beam a best compensating point appears at the vacuum pressure of 1.510*3 Pa. And the neutralization level is advanced with thegrowth of beam current in a constant vacuum pressure. 相似文献
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双离子束溅射沉积薄膜的光学特性与激光损伤研究 总被引:4,自引:1,他引:4
对氧化物薄膜的双离子束溅射沉积作用了系统地实验研究。考察了离子束溅射工艺参数对薄膜光学特性的影响。制备了折射率接近于块材料的TiO2和ZrO2薄膜,显著降低了TiO2,ZrO2和SiO2薄膜的光吸收损耗,TiO2和ZrO2薄膜的抗激光损伤阈值得到显著提高。用双离束溅射沉积1.06μm多层高反,是到了大于99.5%的高反射率,经高温退火处理的双离子束溅射沉积高反膜的抗激光损伤阈值同热蒸发沉积的高反膜 相似文献
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GaN on sapphire was grown by MOCVD technique. Rutherford backscattering spectra together with channeling along [0 0 0 1] axis
were recorded to study the defects at the interface. Detailed calculation shows that the defects at GaN/sapphire interface
are due to dislocations which are distributed into the whole thickness of the film and are mainly aligned on the growth direction. 相似文献
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研究了钝化在抑制电流崩塌的同时,会引起HEMT器件击穿电压的下降.而采用场板结构的AlGaN/GaN场板HEMT器件(FP-HEMT)的击穿电压从46V提高到了148V,表明了场板对提高击穿电压有显著作用(3倍以上).接着,比较了FP-HEMT器件与常规HEMT器件,钝化后HEMT器件在应力前后的电流崩塌程度,得出了采用场板结构比之钝化对器件抑制电流崩塌有更明显作用的结论.从理论上和实验上都表明,采用场板结构能够很好解决提高击穿电压与抑制电流崩塌之间的矛盾.
关键词:
GaN
场板
击穿电压
电流崩塌 相似文献
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在蓝宝石衬底上通过金属有机物化学气相沉积(metal-organic chemical vapor deposition,MOCVD)方法外延生长的GaN薄膜具有良好的结晶品质,χmin达到2.00%. 结合卢瑟福背散射/沟道(Rutherford backscattering/channeling,RBS/C)和高分辨X射线衍射(high-resolution X-ray diffraction,HXRD)的实验测量,研究了不同剂量和不同角度Mg+注入GaN所造成的辐射损伤. 实验结果表明,随注入剂量的增大,晶体的辐射损伤也增大,注入剂量在1×1015atom/cm2以下,χmin小于4.78%,1×1016atom/cm2是Mg+注入GaN的剂量阈值,超过这个阈值,结晶品质急剧变差,χmin达到29.5%;随机注入比沟道注入的辐射损伤大,且在一定范围内随注入角度的增大,损伤也增大,在4×1015atom/cm2剂量下偏离〈0001〉沟道0°,4°,6°,9°时的χmin(%)分别为6.28,8.46,10.06,10.85;经过700℃/10min+1050℃/20s两步退火和1000℃/30s高温快速退火后,晶体的辐射损伤都有一定程度的恢复,而且1000℃/30s高温快速退火的效果更好,晶体的辐射损伤可以得到更好的恢复.
关键词:
GaN
卢瑟福被散射/沟道
高分辨X射线衍射
辐射损伤 相似文献
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Structure and luminescence of a-plane GaN on r-plane sapphire substrate modified by Si implantation 下载免费PDF全文
Lijie Huang 《中国物理 B》2021,30(5):56104-056104
We show the structural and optical properties of non-polar a-plane GaN epitaxial films modified by Si ion implantation. Upon gradually raising Si fluences from 5×1013 cm-2 to 5×1015 cm-2, the n-type dopant concentration gradually increases from 4.6×1018 cm-2 to 4.5×1020 cm-2, while the generated vacancy density accordingly raises from 3.7×1013 cm-2 to 3.8×1015 cm-2. Moreover, despite that the implantation enhances structural disorder, the epitaxial structure of the implanted region is still well preserved which is confirmed by Rutherford backscattering channeling spectrometry measurements. The monotonical uniaxial lattice expansion along the a direction (out-of-plane direction) is observed as a function of fluences till 1×1015 cm-2, which ceases at the overdose of 5×1015 cm-2 due to the partial amorphization in the surface region. Upon raising irradiation dose, a yellow emission in the as-grown sample is gradually quenched, probably due to the irradiation-induced generation of non-radiative recombination centers. 相似文献
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I. M. Tiginyanu V. Popa M. A. Stevens‐Kalceff D. Gerthsen P. Brenner D. Pavlidis 《固体物理学:研究快报》2012,6(4):148-150
We report the maskless fabrication of ultrathin suspended GaN membranes designed by focused ion beam treatment of the GaN epilayer surface with subsequent photoelectrochemical etching. This technological approach allows the fabrication of ultrathin membranes, as well as supporting micro/nanocolumns in a controlled fashion. The analysis of the spatial and spectral distribution of microcathodoluminescence demonstrates that the membranes exhibit mainly yellow luminescence. These results pave the way for the fabrication of ultrathin suspended GaN membranes for MEMS/NEMS applications.
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Limin Zhang Xiaodong Zhang Wei You Zhen Yang WenXiu Wang Qing Ge Zhengmin Liu 《Central European Journal of Physics》2008,6(2):283-288
The effects of Si, O, C and N ion implantation with different implantation doses on yellow luminescence (YL) of GaN have been
investigated. The as-grown GaN samples used in the work were of unintentional doped n-type, and the photoluminescence (PL)
spectra of samples had strong YL. The experimental results showed that YL of ion implanted samples exhibited marked reductions
compared to samples with no implantation, while the near band edge (NBE) emissions were reduced to a lesser extent. The deep-level
centers associated with YL may be produced in GaN films by O and C ion implantation, and identities of these deep-level centers
were analyzed. It was also found that the dose dependence of YL was analogous with the one of the intensity ratios of YL to
the near band edge (NBE) emission (I
YL
/I
NBE
) for ion implanted samples. The possible reason for this comparability has been proposed.
相似文献
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N. Zainal S.V. Novikov A.V. Akimov C.R. Staddon C.T. Foxon A.J. Kent 《Physica B: Condensed Matter》2012,407(15):2964-2966
The dependence of the hexagonal fraction with thickness in MBE-grown bulk cubic (c-) GaN epilayer is presented in this paper. A number of c-GaN epilayers with different thicknesses were characterized via PL and XRD measurements. From the PL spectra, the signal due to h-GaN inclusions increases as the thickness of the c-GaN increases. On the contrary, in the XRD diffractogram, c-GaN shows a dominant signal at all thicknesses, and only a weak peak at ∼35° is observed in the diffractogram, implying the existence of a small amount of h-GaN in the c-GaN layer. The best quality of c-GaN is observed in the first 10 μm of GaN on the top of GaAs substrate. Even though the hexagonal content increases with the thickness, the average content remains below 20% in c-GaN layers up to 50 μm thick. The surface morphology of thick c-GaN is also presented. 相似文献
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Epitaxial evolution on buried cracks in a strain-controlled AlN/GaN superlattice interlayer between AlGaN/GaN multiple quantum wells and a GaN template 下载免费PDF全文
Epitaxial evolution of buried cracks in a strain-controlled AlN/GaN superlattice interlayer(IL) grown on GaN template, resulting in crack-free AlGaN/GaN multiple quantum wells(MQW), was investigated. The processes of filling the buried cracks include crack formation in the IL, coalescence from both side walls of the crack, build-up of an MQW-layer hump above the cracks, lateral expansion and merging with the surrounding MQW, and two-dimensional step flow growth.It was confirmed that the filling content in the buried cracks is pure GaN, originating from the deposition of the GaN thin layer directly after the IL. Migration of Ga adatoms into the cracks plays a key role in the filling the buried cracks. 相似文献