Size Control of Nanoscale Silicon Particles Formed in Thermally Annealed A-Si∶H Films and Its Photoluminescence

A method to control the si ze of nanoscale silicon grown in thermally annealed hydrogenated amorphous silico n (a-Si∶H) films is reported. Using the characterizing techniques of micro-Ra man scattering, X-ray diffraction and computer simulation, it is found that the sizes of the formed silicon particles change with the temperature rising rate i n thermally annealing the a-Si∶H films. When the a-Si∶H films have been anne aled with high rising rate( ~100 ℃/s), the sizes of nanoscale silicon particle s are in the range of 1.6~15 nm. On the other hand, if the a-Si∶H films have been annealed with low temperature rising rate(~1 ℃/s), the sizes of nanoscale silicon particles are in the range of 23~46 nm. Based on the theory of crystal nucleation and growth, the effect of temperature rising rate on the sizes of th e formed silicon particles is discussed. Under high power laser irradiation, in situ nanocrystallization and subsequent nc-Si clusters are small enough for vis ible light emission, authors have not detected any visible photoluminescence(PL) from these nc-Si clusters before surface passivation. After electrochemical ox idization in hydrofluoric acid, however, intense red PL has been detected. Cycli c hydrofluoric oxidization and air exposure can cause subsequent blue shift in t he red emission. The importance of surface passivation and quantum confinement i n the visible emissions has been discussed.     

热处理升温快慢对非晶硅中形成的纳米硅粒尺寸的影响

含氢非晶硅薄膜经过快速热退火处理后,我们用拉曼散射和X-射线衍射技术对样品进行分析.我们的实验结果表明:在非晶硅薄膜中形成的纳米硅晶粒的大小随着热退火过程中升温快慢而变化.在升温过程中,当单位时间内温度变化量较大时（～100℃/s）,则所形成纳米硅粒较小（～1.6～15nm）;若单位时间内温度变化量较低（～1℃/s）,则纳米硅粒较大（～23～46nm）。根据分形生长理论和计算机模拟,我们讨论了升温快慢与所形成的纳米硅颗粒大小的关系.     

氢化非晶硅薄膜退火形成的纳米硅粒

报道了氢化非晶硅薄膜在600～620℃温度下快速退火10s可以形成纳米晶硅,其喇曼散射表明,在所形成的纳米晶硅在薄膜中分布是随机的,其直径在1.6～15nm以内.并且在强光照射下观察了纳米晶硅在薄膜中的结晶和生长情况.     

利用快速退火法控制非晶硅薄膜中纳米硅粒尺寸

报道了利用快速退火法控制膜中纳米硅粒大小的方法,讨论了升温快慢与所形成的纳米硅粒大小的关系.     

Size Control of Nanoscale Silicon Particles Formed in Thermally Annealed A-Si ： H Films and Its Photoluminescence

A method to control the size of nanoscale silicon grown in thermally annealed hydrogenated amorphous silicon （a-Si：H） films is reported. Using the characterizing techniques of micro-Raman scattering, X-ray diffraction and computer simulation, it is found that the sizes of the formed silicon particles change with the temperature rising rate in thermally annealing the a-Si ： H films. When the a-Si：H films have been annealed with high rising rate（～100℃/s）, the sizes of nanoscale silicon particles are in the range of 1.6～15nm. On the other hand, if the a-Si：H films have been annealed with low temperature rising rate（～1℃/s）, the sizes of nanoscale silicon particles are in the range of 23～46nm. Based on the theory of crystal nucleation and growth, the effect of temperature rising rate on the sizes of the formed silicon particles is discussed. Under high power laser irradiation, in situ nanocrystallization and subsequent nc-Si clusters are small enough for visible light emission, authors have not detected any visible photoluminescence（PL） from these nc-Si clusters before surface passivation. After electrochemical oxidization in hydrofluoric acid, however, intense red PL has been detected. Cyclic hydrofluoric oxidization and air exposure can cause subsequent blue shift in the red emission. The importance of surface passivation and quantum confinement in the visible emissions has been discussed.     

Identification of Nucleation Center Sites in Thermally Annealed Hydrogenated Amorphous Silicon

Utilizing the concepts of a critical crystallite size and local film inhomogeneity, it is shown that nucleation in thermally annealed hydrogenated amorphous silicon occurs in the more well ordered spatial regions in the network, which are defined by the initial inhomogeneous H distributions in the as‐grown films. Although the film H evolves very early during annealing, the local film order is largely retained in the still amorphous films even after the vast majority of the H is evolved, and the more well ordered regions which are the nucleation center sites for crystallization are those spatial regions which do not initially contain clustered H, as probed by H NMR spectroscopy. The sizes of these better ordered regions relative to a critical crystallite size determine the film incubation times (the time before the onset of crystallization). Changes in film short range order upon H evolution, and the presence of microvoid type structures in the as grown films play no role in the crystallization process. While the creation of dangling bonds upon H evolution may play a role in the actual phase transformation itself, the film defect densities measured just prior to the onset of crystallization exhibit no trends which can be correlated with the film incubation times.     

a-SiH 热处理过程中纳米硅粒尺寸的控制(英文)

报道了控制热处理过程中含氢非晶硅中纳米硅颗粒大小的一种新方法。用喇曼散射、X射线衍射和计算机模拟,发现在非晶硅中所形成的纳米硅颗粒的大小,随着热退火过程中升温速率的变化而变化。在退火过程中,若非晶硅薄膜升温速率较高(～100℃/s),则所形成纳米硅粒的大小在1.6～15nm;若非晶硅薄膜升温速率较低(～1℃/s),则纳米硅粒大小在23～46nm。根据晶体生长理论,讨论了升温速率的高低与所形成的纳米硅颗粒大小的关系。     

a-Si:H热处理过程中形成的纳米硅粒及其光致发光

报道了氢化非晶硅薄膜在600～620℃温度下快速退火10 s可以形成纳米晶硅,其拉曼散射表明,所形成的纳米晶硅在薄膜中的分布是随机的,其直径在1.6～15 nm内.根据晶体生长理论和计算机模拟,讨论了升温快慢与所形成纳米硅颗粒大小之间的关系,并且在强光照射下观察了纳米晶硅在薄膜中的结晶和生长情况.经退火形成的nc-Si可见光辐射较弱,不能检测到它们的光致发光,但用氢氟酸腐蚀钝化后则可检测到较强的红PL,并且钝化后的nc-Si在空气中暴露一定时间后,其辐射光波长产生了蓝移.就表面钝化和量子限制对可见光辐射的重要性作了讨论.     

用ECRCVD法制备的纳米碳化硅薄膜及其室温下的强光发射

用电子回旋共振化学气相沉积(ECRCVD)方法制备了纳米碳化硅薄膜.实验中发现:在高氢稀释反应气体和高微波功率条件下,可以得到结构上具有纳米碳化硅晶粒镶嵌在碳化硅无序网络中的薄膜.用高分辩透射电子显微镜、傅里叶红外吸收谱、Raman散射和X射线光电子谱等分析手段对薄膜的结构进行了分析.在室温条件下,薄膜能够发出强烈的短波长可见光,发光峰位于能量为2.64eV处.瞬态光谱研究表明样品的光致发光寿命为纳秒数量级,表现出直接跃迁复合的特征.这种材料有希望在大面积平面显示器件中得到应用.     

Raman Scattering and Photoluminescence in Ge-implanted GaN Films

The investigations on Ge-implanted GaN films grown by MOCVD and then annealed at 1100℃ under ammonia ambient have been carried out. With increasing Ge implantation dose, four additional peaks arise at wave numbers of 260, 314, 428 and 670cm-1 in Ramam spectra. In PL spectra, the relative intensity of the band-edge emission compared to the PL-band centered at 2.66eV and the yellow band decreases with increase of Ge-implanted dose. The modes of 260 and 314cm-1 are attributed to disorder-activated Raman scattering, whereas the modes of 428 and 670cm-1 are assigned to local vibrations of vacancies and vacancy-related complexes. The PL-band centered at 2.66eV and the yellow band is also related to these vacancy defects. The new Raman peak at 301cm-1 for the sample annealed only 5min originates from Ge clusters due to deficient annealing.     

利用热退火法从非晶硅薄膜中生长纳米硅粒

报道了一种从氢化非晶硅薄膜中生长纳米硅粒的方法.氢化非晶硅薄膜经过不同条件的热退火处理后,用拉曼散射和X射线衍射技术对样品进行了分析.实验结果表明:在快速升温条件下所形成的nc-Si在薄膜中的分布是随机均匀的,直径在1.6～15 nm范围内,硅粒大小随退火过程中升温快慢而变化.     

石墨上多晶硅薄膜的制备及择优取向的调控

利用磁控溅射在石墨衬底上制备了非晶硅薄膜,并使用快速热退火对薄膜进行了晶化处理。XRD分析表明,直接溅射沉积在石墨衬底上的硅薄膜经过快速热退火后具有高度的(220)择优取向。通过在硅薄膜和石墨衬底界面处引入一定厚度的ZnO中间层,晶化后的多晶硅薄膜择优取向实现了从(220)向(400)的转变,从而非常有利于将成熟的制绒工艺应用于该材料体系的电池制备过程中。对于择优取向的转变提出了解释,认为Si(100)面和ZnO(001)面晶格匹配是主要原因。喇曼分析表明ZnO中间层的引入提高了多晶硅薄膜的晶体质量。     

纳米硅镶嵌氮化硅薄膜的制备与光致发光特性

为研究氮化硅薄膜发光材料的制备工艺及其光致发光机制,实验采用射频磁控反应溅射技术与热退火处理制备了纳米硅镶嵌氮化硅薄膜材料.利用红外光谱(IR)、X射线衍射谱(XRD)、能谱(EDS)和光致发光谱(PL),对不同工艺条件下薄膜样品的成分、结构和发光特性进行研究,发现在制备的富硅氮化硅薄膜材料中形成了纳米硅颗粒,并计算出其平均尺寸.在510 nm光激发下,观察到纳米硅发光峰,对样品发光机制进行了讨论,认为其较强的发光起因于缺陷态和纳米硅发光.     

GaN:Si薄膜的结构和应力特性研究

对掺杂浓度为1017～1019cm-3的GaN:Si样品进行高精度X射线衍射和拉曼散射光谱的研究发现:随着Si掺杂浓度的增加,GaN晶粒尺寸逐渐减小,引发更多的螺位错和混合位错致使摇摆曲线的半高宽有所增加,同时薄膜中的剩余应力也逐渐减小。当掺杂浓度高于2.74×1018cm-3时,薄膜从压力状态转变为张力状态。     

嵌入在Si衬底上的分子束外延GaAs层的微区喇曼和光致发光分析

对分子束外延生长的嵌入在Si衬底上的边长为20—150μm正方形GaAs层微区进行了微区喇曼和光致发光分析。发现微区GaAs层的喇曼散射谱和光致发光谱与普通平面Si片上生长的GaAs层的基本相同,证实嵌入式生长可以得到与通常平面生长基本相同的质量。仔细的分析表明随着微区尺寸的减小GaAs层的无序程度有少许增长。     

铒,氧共注a—Si：H和a—SiCx：H的1.54μm光致发光

在ａ－Ｓｉ：Ｈ和ａ－ＳｉＣｘ：Ｈ中共注稀土铒和氧。３００℃和４００℃热退火后，测得了来自发光中心Ｅｒ３＋内层４ｆ电子跃迁的１．５４μｍ光致发光。４００℃是较好的退火温度。随着碳含量的增加，发光强度逐渐减弱，这可能是由于碳的引入减弱了间隙氧退火时的迁移能力所致。     

微晶硅薄膜太阳电池中孵化层研究

对甚高频等离子体增强化学气相沉积技术制备的微晶硅薄膜太阳电池进行了研究.喇曼测试结果显示:微晶硅薄膜太阳电池在p/i界面存在着一定的非晶孵化层.孵化层的厚度随硅烷浓度的增加或辉光功率的降低而增大.可以通过适当的硅烷浓度或适当的辉光功率来降低孵化层的厚度.     

非晶硅薄膜的镍诱导横向晶化工艺及其特性

报道了镍诱导非晶硅薄膜的晶化技术 ,探讨了镍诱导晶化机理 .详细调查了诱导晶化时间和温度对晶化速率的影响 ,并用 Raman、AFM和 TEM等测试了材料的特性 .实验结果发现用该方法可以获得较大晶粒的多晶 ;在晶化温度为 6 2 5℃左右时晶体横向晶化速率最高 .如要获得较长的晶体 ,低温退火则比较有利     

在Si(111)上磁控溅射碳化硅薄膜的H2退火效应

用射频磁控溅射法在常温硅衬底上制备了碳化硅薄膜并研究了氢退火对薄膜的影响.用傅里叶红外透射谱(FTIR)、X射线衍射(XRD)、X光电子能谱(XPS)、扫描电镜(SEM)及原子力显微镜(AFM)对薄膜样品进行了结构、组分和形貌分析.结果表明:高温退火后SiC膜的晶化程度明显提高,而且在薄膜中观察到了碳纳米线的形成.     

本征微晶硅薄膜的结构演变及其对太阳电池光伏性能的影响

采用高压射频等离子体增强化学气相沉积（RF-PECVD）方法制备本征硅薄膜和n-i-p结构太阳电池,研究了氢稀释率对本征硅薄膜的电学特性和结构特性的影响. 采用光发射谱（OES）和喇曼（Raman）散射光谱研究了处于过渡区的本征硅薄膜的纵向结构演变过程. 结果表明：光发射谱和喇曼散射光谱可以作为研究硅薄膜的纵向结构演变有效手段. 随着氢稀释率的增加,硅薄膜从非晶相向微晶相过渡时,其纵向结构的改变会严重影响硅薄膜太阳电池的光伏性能.