常见点缺陷对硅光电池响应特性的影响

研究了硅光电池中常见点缺陷对器件在激光辐照下的响应特性的影响。根据第一性原理建立了晶胞模型,比较了空位缺陷以及含Fe, Cu杂质状态下硅材料的态密度图,在此基础上分析了常见点缺陷对硅光电池响应特性的影响。由于半导体材料对温度敏感,当光电池受激光辐照而出现温度变化时,其光电响应输出特性会发生变化。从光伏器件的光生电动势原理出发,根据响应输出模型以及一维热传导方程,计算了1 064 nm激光辐照下,空位和金属杂质两种本征点缺陷对光电池响应特性的影响规律。结果表明：空位和金属杂质两种缺陷都能够改变硅材料的能带结构和响应特性。当激光辐照波长为1 064 nm,功率密度为4×10⁵ W/cm²时,其中间隙原子为Fe时对材料的电子结构和光学性质的影响最大。此时材料吸收系数高达23 952 cm^-1,且量子效率值最大,导致光电池响应最为强烈,输出电压最小。     

Si掺杂对缺陷诱导的GaN磁性的影响

利用第一性原理局域密度自旋近似方法,研究了缺陷诱导的GaN的内禀磁性以及Si掺杂对缺陷GaN磁性的影响.研究发现缺陷诱导GaN的内禀磁矩为3μB,Si掺杂后缺陷诱导的GaN磁矩发生淬灭为2μB.随Si含量的增加磁矩进一步减少.该理论结果对实验有指导意义.     

添加剂对Fe—Cu系陶瓷材料负阻特性的影响

文章介绍了以Ｆｅ２Ｏ３和Ｃｕ２Ｏ为主成分的陶瓷材料的负阻特性，分析论述了Ｃｏ２Ｏ３、Ｂｉ２Ｏ３以及ＭｎＯ２掺杂对Ｆｅ－Ｃｕ系陶瓷材料负阻性能的影响，实验制得负阻系数ｎ＞１０，电压Ｖｐ＞２００的负阻性能良好的陶瓷材料。     

非晶Fe73.5Cu1Nb3Si13.5B9合金的激光纳米晶化研究

在相同激光扫描速度(20mm／s)和不同激光功率(150W，200W，250W，300W)工艺条件下，利用CO2激光对铁磁Fe73．5Cu1Nb3Si13．5B9非晶带进行了辐照处理，诱导非晶带样品发生纳米晶化。应用穆斯堡尔(Mossbauer)谱(MS)、透射电镜(TEM)和X射线衍射(XRD)对实验样品的晶化工艺、纳米晶相的组织结构、晶化量和纳米晶化机理等进行了研究。结果表明，晶化析出相是α-Fe(Si)单相固溶体，具有4种超精细结构；其晶粒尺寸约为10～20nm；纳米晶均匀分布在非晶基体上，形成非晶相与纳米晶化相的双相组织结构。随着激光功率的增加，纳米晶化量随着增加，可通过控制激光处理工艺参量，来实现纳米晶化量的控制。     

As、Ga掺杂对Mn4Si7电子结构和光学特性的影响

采用基于密度泛函理论的平面波超软赝势方法研究了四方本征Mn4 Si7、As掺杂及Ga掺杂(同一周期不同主族进行n、p型掺杂)Mn4 Si7模型的电子结构以及光学性质.通过对其能带、态密度及光学性质的分析可以发现,As、Ga掺入后引入了杂质能带,能带曲线向低能级方向移动,导致禁带宽度减小,杂质的引入使得其介电常数、吸收率...     

蒸发时间对Mg_2Si薄膜的影响

本文旨在研究Mg_2Si半导体薄膜的制备过程中,蒸发时间对Mg_2Si薄膜的影响。通过采用电阻式热蒸发及退火工艺的制备方法制备了Mg_2Si半导体薄膜。在低真空(10-1~10-2Pa),400℃热处理4h条件下,研究在80A蒸发电流时,不同蒸发时间对Mg_2Si薄膜的影响。并采用扫描电镜手段对实验形成的Mg_2Si薄膜的结构进行了表征。最后得出结论:低真空(10-1~10-2Pa),400℃热处理4h条件下,蒸发时间为16min是制备高质量Mg_2Si半导体薄膜的最佳蒸发时间。     

Si晶体中Cu和Fe杂质在Frank型位错上的不同沉淀行为

本文运用电子束感应电流技术和透射电子显微镜研究了直拉Ｓｉ单晶中Ｃｕ和Ｆｅ杂质在Ｆｒａｎｋ型位错上的沉淀行为．发现尽管在Ｓｉ中Ｃｕ杂质浓度远高于Ｆｅ杂质，但Ｃｕ杂质不沉淀在Ｆｒａｎｋ型位错上，而Ｆｅ杂质会沾污Ｆｒａｎｋ型位错．研究结果表明，样品中微小Ｐｕｎｃｈｅｄ－ｏｕｔ位错的存在和Ｃｕ杂质在Ｓｉ中的重复成核机制是Ｃｕ杂质不沉淀在Ｆｒａｎｋ型位错上的主要原因．     

Cu、Fe对Al-Mn箔腐蚀形貌及比电容量的影响

作者研究了(0.0053～0.82)wt%Cu、(0.032～0.70)wt%Fe对Al-Mn合金箔腐蚀形貌和比电容量(C_s)的影响。测定了Cu-Cs、Fe/Mn-Cs曲线,用SEM(附WDS)观察了箔材腐蚀形貌和箔表面Cu、Fe等元素的分布,用IBAS和TEM(附EDAX)观测了含Fe化合物的参数、成份与高倍形貌。发现Cu在铝箔中有利于形成均匀、细密的蚀孔,使比电容量提高很大。Fe在铝箔中趋向于形成化合物,含大颗粒(d>0.58μm)化合物的铝箔在腐蚀时,箔面形成深而大的蚀孔,造成不均匀腐蚀,但这类化合物的蚀孔大约只有10~8个/cm~2,对箔的比电容量影响较小。     

表面微结构的高响应度Si基近红外光电探测器

为了使Si基光电探测器应用到近红外光波段,需要提升其对光的响应度。通过等离子体光刻在硅基光电探测器表面制备规则有序的微结构阵列,另外通过原子层沉积(ALD)在微结构表面生长一层Al_2O_3膜,研究它的抗反射和钝化作用。对比测量器件的表面反射率和I-V特性曲线,并计算器件在808 nm近红外光下的光响应度。通过计算发现器件的响应度由最初的0.063 A/W提高到0.83 A/W。     

Fe在BaTiO_3(001)表面的吸附状态和成键结构

基于高分辨电子显微镜实验研究,采用第一原理方法系统研究了Fe在BaTiO3(001)不同类型截止表面的吸附状态,解析Fe/BaTiO3界面的原子结构和界面成键性质。研究指出,Fe在BaTiO3(001)表面的吸附强弱与界面Fe—O键有关,Fe在TiO2截止面更能稳定的外延生长;然而,Fe—O在BaO截止面比在TiO2截止面的成键作用更强。     

烧成工艺对Fe-Cu系陶瓷材料负阻特性的影响

通过大量的实验研究证明：Ｆｅ－Ｃｕ系陶瓷材料对烧成温度比较敏感，样品的烧成温区比较窄，只有２０°左右。同一烧成温度下，保温时间越长，负阻特性能越坏，击穿电压、负值系数下降。降温速率对其负阻特性没有多大影响，采取随炉降温即可获得负阻特性较好的样品。     

Distributions of substitutional and interstitial impurities in silicon ingot with different grain morphologies

A multicrystalline silicon ingot with columnar and irregular grains was obtained from metallurgical-grade silicon (MG-Si) by directional solidification. The segregation behaviors of substitutional and interstitial impurities in different grain morphologies have been studied. The concentration distribution of substitutional impurities (B and Al) in the silicon ingot was accord with the Scheil's equation, which depended on the grain morphology. However, the concentration distribution of interstitial impurities (Fe, Ti, Cu, and Ni) was only accord with the Scheil's equation under the columnar grains growth condition. The difference lattice sites of the impurities will result in the disparate segregation behavior of impurities for columnar and irregular grains growth, which leads to the diverse concentration distribution of substitutional and interstitial impurities in the silicon ingot. Furthermore, the transport mechanism of interstitial and substitutional impurities in front of the solid-liquid interface boundary has been revealed.     

The effects of doping impurities and substrate crystallin on the formation of nickel suicides on silicon at 200–280° C

Transmission electron microscopy and Auger electron spectroscopy have been applied to investigate the effects of doping impurities and substrate crystallinity on the formation of nickel suicides at 200–280° C in nickel thin films on silicon. The systems investigated included samples with as-implanted BF₂, B, F, As, and P and recrystallized (001) Si as well as P-doped low pressure chemical vapor deposited (LP-P) and B-doped plasma enhanced chemical vapor deposited (PE-B) amorphous silicon substrates. In samples annealed at 220–280° C, substantial amounts of epitaxial NiSi₂ were found to form on crystalline structure of BF₂, B and F implanted samples to various extents at different temperatures. High resolution lattice imagings of cross-sectional samples showed that the epitaxial NiSi₂/Si interfaces are coherent. No NiSi₂ was detected in all nickel thin films deposited on implantation-amorphous specimens. NiSi₂ epitaxy was found to be a sensitive function of annealing temperature. Good correlation was found between the atomic size factor and resulting stress and NiSi₂ epitaxy at low temperature. The formation of Ni₂Si and NiSi was observed to be influenced by the dopant species and crystallinity of the substrates. The vast difference in inducing the formation of nickel suicides in implantation-amorphous and recrystallized samples is likely due to variations in initial structure and/or dopant distribution. The finding that bothn-type andp-type dopants influenced the formation of Ni₂Si and NiSi suggested that they may be related to the electrical activity of the doping species in recrystallized samples. NiSi, possessing one of the lowest resistivity among all metal silicides, was found to be the only phase formed in all implantation-amorphous as well as LP-P and PE-B amorphous silicon samples annealed at 280° C. Nickel thin film appears to be an attractive candidate for the metallization of amorphous silicon devices.     

CO2激光辐照Fe73.5Cu1Nb3Si13.5B9非晶合金的微量晶化

利用透射穆斯堡尔谱 (TMS)对原始态和晶化后非晶软磁合金Fe73.5Cu1 Nb3Si1 3.5B9进行了结构分析。实验结果表明 ,利用连续CO2 激光处理 ,可使样品的非晶带表面产生少量晶化 ,晶化析出相为Fe Si;在样品的非晶相中发生了磁矩重排 ,原子磁矩在面内取向占优。在一定激光辐照工艺条件下 ,可以控制样品的磁矩变化并实现微量晶化     

Impact of compositional grading and overall Cu deficiency on the near‐infrared response in Cu(In,Ga)Se2 solar cells

Highly efficient thin film solar cells based on co‐evaporated Cu(In,Ga)Se₂ (CIGS) absorbers are typically grown with a [Ga]/([Ga] + [In]) (GGI) gradient across the thickness and a Cu‐poor composition. Upon increasing the Cu content towards the CIGS stoichiometry, lower defect density is expected, which should lead to increased absorption in the near‐infrared (NIR), diffusion length and carrier collection. Further, optimization of the GGI grading is expected to increase the NIR response. In this contribution [Cu]/([In] + [Ga]) (CGI) values are increased by shortening the deposition stage after the first stoichiometric point. In order to obtain comparable Ga contents at the interface for proper band alignment, the front GGI gradings were actively modified. With a relative CGI increase of 7%, we observe an increased photocurrent, originating from an improved NIR external quantum efficiency response. By characterizing the modified absorber properties by reflection‐transmission spectroscopy, we attribute the observed behavior to changes in the optical properties rather than to improved carrier collection. Cu‐dependent modifications of the NIR‐absorption coefficients are likely to be responsible for the variations in the optical properties, which is supported by device simulations. Adequate re‐adjustments of the co‐evaporation process and of the alkali‐fluorides post‐deposition treatments allow maintaining V_oc and FF values, yielding an overall increase of efficiency as compared to a reference baseline. © 2016 The Authors. Progress in Photovoltaics : Research and Applications published by John Wiley & Sons Ltd.