纳米GaP材料Ga填隙缺陷的EPR实验观察

利用电子顺磁共振(EPR)技术对纳米GaP粉体材料的本征点缺陷进行了研究，结果表明：由EPR信息的g因子值（2.0027±0.0004）可以确定纳米GaP粉体材料存在Ga自填隙（Ga_i）本征缺陷；纳米GaP粉体EPR信号超精细结构消失，以及谱线线宽（ΔH_PP）变窄等实验现象，可能是由纳米材料界面的无序性，以及缺陷原子和界面原子之间的电子交换造成的；在较低的测试温度范围内，升高温度引起纳米GaP材料发生晶界结构弛豫；当测试温度由100 K升高至423 K时，ΔH_PP值和自由基浓度皆逐渐降低.     

掺铒GaN薄膜的背散射/沟道分析和光致发光研究

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     

退火对多晶ZnO薄膜结构与发光特性的影响

用射频反应溅射法在Si（111）衬底上制备了C轴取向的多晶ZnO薄膜，通过不同温度的退火处理，研究了退火对多晶ZnO薄膜结构和发光特性的影响.由x射线衍射得知，随退火温度的升高，晶粒逐渐变大，薄膜中压应力由大变小至出现张应力.光致发光测量发现，样品在430nm附近有一光致发光峰, 峰的强度随退火温度升高而减弱，联合样品电阻率随退火温度升高而逐渐变大的测量及能级图，推测出ZnO薄膜中的蓝光发射主要来源于锌填隙原子缺陷能级与价带顶能级间的跃迁. 关键词： ZnO薄膜 退火 光致发光 射频反应溅射     

退火对非故意掺杂4H-SiC外延材料386 nm和388 nm发射峰的影响

10 K条件下,采用光致发光(PL)技术研究了不同退火处理后非故意掺杂4H-SiC外延材料的低温PL特性.结果发现,在370—400 nm范围内出现了三个发射峰,能量较高的峰约为3.26 eV,与4H-SiC材料的室温禁带宽度相当.波长约为386 nm和388 nm的两个发射峰分别位于~3.21 eV和~3.19 eV,与材料中的N杂质有关.当退火时间为30 min时,随退火温度的升高,386 nm和388 nm两个发射峰的PL强度先增加后减小,且退火温度为1573 K时,两个发射峰的PL强度均达到最大. 关键词： 光致发光 退火处理 能级 4H-SiC     

PbWO4闪烁晶体的辐照损伤机理研究

完成了６４０—１０４０℃温度范围内钨酸铅［ＰｂＷＯ４（ＰＷＯ）］晶体的退火实验,观察到较低温退火时晶体中本征色心吸收带（３５０ｎｍ）先是增加,其后随退火温度的升高而逐渐降低直至消除的全过程．分析了ＰＷＯ晶体的本征缺陷和电荷补偿机制．讨论了退火过程中氧进入晶体后色心的产生和转化规律,并提出可能发生Ｐｂ３＋→Ｐｂ４＋的进一步氧化过程,从而导致Ｐｂ３＋空穴中心的湮没．测量并比较了不同退火温度处理后ＰＷＯ晶体的紫外辐照诱导色心吸收谱．观察到导致辐照损伤的Ｏ－空穴中心主要来自晶体中固有的Ｐｂ３＋空穴中心向Ｏ－空穴中心的转化;同时晶体中氧空位作为电子陷阱对Ｏ－空穴中心有稳定作用．当上述两项因素得以消除,晶体辐照硬度随之提高．实验表明,在含氧气氛中高温退火可以有效地改进ＰＷＯ晶体的抗辐照损伤能力．铁杂质对ＰＷＯ的抗辐照能力十分有害     

磷离子注入纳米金刚石薄膜的n型导电性能与微结构研究

系统研究了磷离子注入并在不同温度退火后的纳米金刚石薄膜的微结构和电学性能.研究表明,当退火温度达到800 ℃以上时,薄膜呈良好的n型电导.Raman光谱和电子顺磁共振谱的结果表明,薄膜中金刚石相含量越高和完整性越好,薄膜电阻率越低. 这说明纳米金刚石晶粒为薄膜提供了电导.1000 ℃退火后,薄膜晶界中的非晶石墨相有序度提高,碳悬键数量降低,薄膜电阻率升高.薄膜导电机理为磷离子注入的纳米金刚石晶粒提供了n型电导,非晶碳晶界为其电导提供了传输路径. 关键词： 纳米金刚石薄膜 n型 磷离子注入     

氧压对飞秒激光沉积ZnO/Si(100)薄膜光学性能的影响

利用飞秒脉冲激光沉积法在n-Si（100）单晶衬底上制备了ZnO薄膜, 分析了衬底温度、激光能量、氧压及退火处理对薄膜结构和光学性能的影响. X射线衍射结果表明, 当激光能量为15?mJ、氧压为10?mPa时, 80?℃生长的薄膜取向性最好. 场扫描电子显微镜结果显示薄膜的晶粒尺寸随激光能量的增加而减小、随衬底温度的升高而增大且退火后明显变大. 紫外-可见透射光谱显示薄膜具有90%以上的可见光透过率.光致发光谱表明当氧压为10 mPa时,除了ZnO的紫外本征峰外, 还有一波长为410 nm的强紫光峰, 当氧压增至20 mPa以上, 所有缺陷峰均消失, 只有376 nm处的紫外本征峰. 与纳秒激光法所制备的薄膜特性进行了比较, 结果表明, 虽然纳秒激光沉积所制备的薄膜具有更高的c轴取向度, 但飞秒激光沉积制备的薄膜具有更好的发光性能. 关键词： 氧化锌 飞秒脉冲激光沉积 透过率 光致发光     

低维黑磷的合成及其抗氧化研究

二维黑磷（2D-BP）和黑磷量子点（BP-QDs）等低维黑磷材料在结构和光电性能方面表现出巨大的潜在应用价值,但其仍面临着合成不可控和抗氧化性差等问题。通过引入微波法实现了低维黑磷的简便、低成本合成;研究了微波退火温度和退火时间对低维黑磷结构、形貌和光致发光性能的影响;通过原子层沉积法在BP-QDs样品表面沉积氧化铝（Al₂O₃）保护层,研究了Al₂O₃薄膜厚度对BP-QDs抗氧化性的影响。结果表明：随着微波退火温度的增加,量子点尺寸逐渐减小,光致发光发射峰出现蓝移,这说明反应温度会影响材料的尺寸,进而影响其带隙和光致发光特性;当微波退火时间持续增加时,黑磷纳米片被逐渐剥离并形成BP-QDs;当微波退火温度和时间分别为250℃和4 h时,BP-QDs分布均匀且尺寸更小;随着Al₂O₃膜厚的增加,保护性能越来越好;当Al₂O₃薄膜厚度为20 nm时,BP-QDs在空气中的抗氧化性最佳。     

LPCVD法制备的高纯半绝缘4H-SiC晶体ESR谱特性

利用电子自旋共振波谱（ESR）仪,分析由低压化学气相沉积（LPCVD）法制备的高纯半绝缘4H-SiC材料本征缺陷.结果发现,在暗场条件下获得的缺陷信息具有碳空位（V_C）及其络合物的特征;谱线具有半高宽较大、峰谷明显不对称的特点.分析认为造成ESR谱线半高宽较大及峰谷不对称现象的主要原因是测试温度较高.同时,吸收谱中峰谷不对称现象及较大半高宽现象的出现还与不对称的晶格结构及缺陷浓度的不均匀分布有关.在110 K测试温度下,能级上的电子分布对ESR谱特性影响很小. 关键词： 低压化学气相沉积 高纯半绝缘4H-SiC 电子自旋共振 本征缺陷     

高剂量Ar离子辐照Si缺陷产生及其退火行为EPR研究

112MeVAr离子在50K以下的低温辐照Si到8×10¹⁴/cm²剂量,室温下采用电子顺磁共振技术分析了由辐照引起的缺陷产生及其退火行为,结果表明:Ar离子辐照在Si中引起了中性四空位(Si-P3心)､带正电荷的〈100〉劈裂的双间隙子(Si-P6心)以及连续的非晶层3种缺陷的形成. 在200℃的退火温度,Si-P3心和Si-P6心消失,这时带负电荷的五空位(Si-P1心)开始生长,Si-P1心可以保持到550℃左右的退火温度. 在350℃时,可以明显地观测到另一个含有更多空位的顺磁缺陷心(Si-A11心).连续非晶层的再结晶需要600℃以上的温度,并且在整个退火过程中,非晶顺磁共振线的线型和线宽保持不变. 定性地讨论了结果.     

Relationship of annealing time and intrinsic defects of unintentionally doped 4H-SiC

With annealing temperature kept at 1573 K, the effects of annealing time on stability of the intrinsic defects in epitaxial unintentionally doped 4H-SiC prepared by low pressure chemical vapour deposition have been studied by electron spin resonance (ESR) and low temperature photoluminescence. This paper reports the results shown that annealing time has an important effect on the intrinsic defects in unintentionally doped 4H-SiC when annealing temperature kept at 1573 K. When the annealing time is less than 30 min, the intensity of ESR and photoluminescence is increasing with annealing time prolonged, and reaches the maximum when annealing time is 30 min. Then the intensity of ESR and photoluminescence is rapidly decreased with the longer annealing time, and much less than that of as-grown 4H-SiC when annealing time is 60 min, which should be related with the interaction among the intrinsic defects during the annealing process.     

Comparison between cathodoluminescence spectroscopy and capacitance transient spectroscopy on Al+ ion implanted 4H-SiC p+/n diodes

The comparison between cathodoluminescence and deep level transient spectroscopy is a powerful tool to analyze the defect formation in implanted materials. In this work aluminium implanted 4H-SiC p⁺/n diodes are studied. Different structures, implanted with different ion energy and fluencies, are analyzed in order to understand the process related effects. The comparison between the epilayer and the implanted areas shows an increase of the concentration of intrinsic defects in the implanted areas. The 4H-SiC band-edge emission decreases, increasing the aluminium ion dose, due to the enhancement of the lattice disorder, partially recovered by the post-implantation annealing.     

Defect Characterization of 6H-SiC Studied by Slow Positron Beam

利用单能慢正电子束流,对原生的和经过电子辐照的6H-SiC内的缺陷形成及其退火行为进行研究．发现在n型6H-SiC中,经过退火后缺陷浓度降低．这主要是因为在退火过程中缺陷和间隙子的相互作用所引起．n型6H-Si经过1400 oC、30 min真空退火后,在SiC表面形成一个大约20 nm的Si层,这是在高温退火过程中Si原子向表面逸出的有力证明．在高温退火中,在样品的近表面区域有一个明显的表面效应,既在这些区域的S参数整体较大,这种现象与高温退火中Si不断向表面逸出有关．经过10 MeV的电子辐照,在n型6H-SiC中,正电子有效扩散长度从86.2 nm减少至39.1 nm,说明在样品中由于电子辐照产生大量缺陷．但是对p型6H-SiC,经过10 MeV电子辐照后有效扩散长度变化不大,这与其中缺陷的正电性有关．同时还对n型6H-SiC进行了1.8 MeV电子辐照后的300 oC退火实验,发现退火后缺陷浓度不减反增,这主要是因为在退火过程中,一些双空位缺陷和Si间隙子互相作用从而产生了VC缺陷的缘故．     

不同极性6H-SiC表面石墨烯的制备及其电子结构的研究

在超高真空设备中,采用高温退火的方法在6H-SiC两个极性面(0001)和(000 1 - )面(即Si面和C面)外延石墨烯(EG). 利用低能电子衍射(LEED)和同步辐射光电子能谱(SRPES)对样品的生长过程进行了原位研究,而后利用激光拉曼光谱(Raman)和近边X射线吸收精细结构(XANES)等实验技术对制备的样品进行了表征. 结果表明我们在两种极性面均制备出了质量较好的石墨烯样品. 而有关两种石墨烯的对比性研究发现:Si面EG呈同一取向而C面EG呈各向异性;Si面EG与衬底存在类似 关键词： 石墨烯 6H-SiC 同步辐射 电子结构     

Effects of implantation defects on the carrier concentration of 6H-SiC

The effects of ion irradiation defects on the carrier concentration of 6H-SiC epitaxial layer were studied by current–voltage (I–V), capacitance.-voltage (C–V) measurements, thermally stimulated capacitance and deep level transient spectroscopy. The defects were produced by irradiation with 10 MeV C⁺ at a fluence of 10¹¹ ions/cm² and subsequent thermal annealings were carried out in the temperature range 500–1700 K under N₂ flux. I–V and C–V measurements reveal the presence of a high defect concentration after irradiation and annealing at temperature lower than 1000 K. Thermally stimulated capacitance measurements show that some of the defects induce a deactivation of the nitrogen donor, while some of the generated defects, behaving as donor-like traps, contribute to increase the material free carrier concentration at temperatures above their freezing point. Deep level transient spectroscopy measurements performed in the temperature range 150–450 K show the presence of several overlapping traps after ion irradiation and annealing at 1000 K: these traps suffer a recovery and a transformation at higher temperatures. The annealing of all traps at temperatures as high as 1700 K allows one to completely restore the n-type conductivity. The defects mainly responsible of the observed change in the carrier concentration are identified. PACS 73.30.+y; 61.80.Jh; 61.82.Fk; 85.30.Hi     

4H-SiC同质外延的绿带发光与缺陷的关系

利用室温光致发光谱(PL)对CVD法生长的4H-SiC同质外延特性进行研究,发现有绿带发光(GL)特性.用扫描电子显微镜(SEM) 、二次离子质谱(SIMS)和X射线光电子谱(XPS)技术获得了4H-SiC样品纵截面形貌和元素相对含量分布.结果表明,GL与4H-SiC晶体中碳空位(V_C)及络合体缺陷相关,V_C和缓冲层的扩展缺陷(点缺陷和刃位错等)是GL微观来源.GL的半峰宽(FWHM) 反映了参与复合发光的V_C及其络合缺陷能级分散的程度.室温下获得的样品GL强度和光谱波长度可用于分析4H-SiC外延中缺陷分布和晶体质量. 关键词： 绿带发光 4H-SiC同质外延 晶体缺陷     

Study on structural properties of epitaxial silicon films on annealed double layer porous silicon

In this paper, epitaxial silicon films were grown on annealed double layer porous silicon by LPCVD. The evolvement of the double layer porous silicon before and after thermal annealing was investigated by scanning electron microscope. X-ray diffraction and Raman spectroscopy were used to investigate the structural properties of the epitaxial silicon thin films grown at different temperature and different pressure. The results show that the surface of the low-porosity layer becomes smooth and there are just few silicon-bridges connecting the porous layer and the substrate wafer. The qualities of the epitaxial silicon thin films become better along with increasing deposition temperature. All of the Raman peaks of silicon films with different deposition pressure are situated at 521 cm⁻¹ under the deposition temperature of 1100 °C, and the Raman intensity of the silicon film deposited at 100 Pa is much closer to that of the monocrystalline silicon wafer. The epitaxial silicon films are all (4 0 0)-oriented and (4 0 0) peak of silicon film deposited at 100 Pa is more symmetric.     

Assessing the effect of hydrogen on the electronic properties of 4H-SiC

As a common impurity in 4H silicon carbide (4H-SiC), hydrogen (H) may play a role in tuning the electronic properties of 4H-SiC. In this work, we systemically explore the effect of H on the electronic properties of both n-type and p-type 4H-SiC. The passivation of H on intrinsic defects such as carbon vacancies (V_C) and silicon vacancies (V_Si) in 4H-SiC is also evaluated. We find that interstitial H at the bonding center of the Si-C bond (H_i^bc) and interstitial H at the tetrahedral center of Si (H_i^Si-te) dominate the defect configurations of H in p-type and n-type 4H-SiC, respectively. In n-type 4H-SiC, the compensation of H_i^Si-te is found to pin the Fermi energy and hinder the increase of the electron concentration for highly N-doped 4H-SiC. The compensation of H_i^bc is negligible compared to that of V_C on the p-type doping of Al-doped 4H-SiC. We further examine whether H can passivate V_C and improve the carrier lifetime in 4H-SiC. It turns out that nonequilibrium passivation of V_C by H is effective to eliminate the defect states of V_C, which enhances the carrier lifetime of moderately doped 4H-SiC. Regarding the quantum-qubit applications of 4H-SiC, we find that H can readily passivate V_Si during the creation of V_Si centers. Thermal annealing is needed to decompose the resulting V_Si-nH (n=1-4) complexes and promote the uniformity of the photoluminescence of V_Si arrays in 4H-SiC. The current work may inspire the impurity engineering of H in 4H-SiC.