ZnSe单晶的气相生长及光学性质

用改进的化学气相输运技术(CVT),以Zn(NH4)3Cl5为新的气相输运剂,直接从单质Zn和Se一步在封密管中生长了ZnSe单晶,升华温度1001～1020℃,管内温差<4℃。经过两周生长,得到8mm×7mm×0.8mm的绿色ZnSe晶体。XRD表明晶体表面为(111)面;受气固界面形貌影响,双晶衍射半高峰宽为50s;PL谱由DPA和SA两个发光峰组成;并研究了晶体片的吸收光谱、荧光光谱、反射光谱和红外透过等光学性质。     

以Zn(NH4)3Cl5为输运剂气相生长ZnSe单晶

以化合物Zn(NH4)3Cl5为气相输运剂,ZnSe多晶为原料,用化学气相输运技术(CVT)在封闭石英管中生长出直径9 m m、长度25 mm的Zn1+0 031Se单晶晶体生长区的温度为898～915℃,温度梯度为1.5℃@cm-1,生长周期为21 d.晶体生长端由{111}和{100}单形包围.用RO-XRD技术研究了晶体的结晶质量,ZnSe(111)的RO-XRD谱的FWHM为24 s.光致发光特性研究表明,Zn1+0.031Se单晶体的PL谱由Fx(439 nm)和BBT(418 nm)等发光峰组成,晶体的短波吸收限位于465 nm处,腐蚀点密度为(5～7)×104cm-2.化合物Zn(NH4)3Cl5具有较高的热稳定性,是一种适合气相生长ZnSe单晶的新型输运剂.     

大功率激光窗口ZnSe的制备原理及方法

比较了四种适用于作CO2激光器窗口的材料,Ge、KCl、GaAs和ZnSe,指出ZnSe是大功率激光器最理想的窗口材料,并列举了3种ZnSe的制备原理及方法,阐述了CVD方法制备多晶ZnSe的过程.     

水溶液法制备CdSe和ZnSe纳米棒

用水溶液法直接合成了水溶性、发荧光的ZnSe和CdSe纳米棒。ZnSe纳米棒的直径约20～30nm,长度可达60～70nm;CdSe纳米棒的直径约30～60nm,长度可达150～450nm。用X射线衍射仪(XRD)、透射电镜(TEM)、高分辨透射电镜(HR-TEM)、荧光仪等仪器对纳米棒进行了表征。XRD和HRTEM的结果显示纳米棒具有立方结构,结晶度较高。讨论了纳米棒的形成机理以及pH对纳米棒发光强度的影响。合成的纳米棒在水溶液中至少稳定半年,表面被氨基和羧基化,在生物分析中具有广泛的应用前景。     

水热合成法制备纳米磷灰石晶体比较研究

用水热合成方法在不同条件下制备了纳米级磷灰石晶体。结果表明：磷灰石晶体含有0H^-、CO3^2-、Na^ 、HPO4^2-离子；水热合成时温度越高，反应时间越长，磷灰石结晶度越高，晶体生长得更大更长；磷灰石沉积物老化时间越短，表面活性越高，水热处理时更容易生长成较大的晶体；压力条件下水热处理后的磷灰石晶体呈棒状，常压下水热处理的呈针状，且长径比较大。     

化学气相沉积（CVD）法制晶体金刚石的机理

引言现在正用低压气体来制造晶体金刚石而不是过去传统考虑的高温高压。生产金刚石的气相沉积过程所用的温度和压力条件对碳来说其稳定形式是石墨。然而,动力学因素允许通常是纯化学反应来形成的金刚石     

热丝法制备多晶硅薄膜晶体取向及形态的研究

采用热丝化学气相沉积法(HWCVD),在很近的热丝与衬底距离(5 mm)下沉积多晶硅薄膜,研究了热丝温度、SiH4浓度对多晶硅晶粒取向和晶粒尺寸的影响规律。结果表明:当热丝温度在1400℃~1800℃变化,衬底温度225℃~320℃时,沉积出多晶硅薄膜的择优取向随温度升高的变化规律是(111)→(220)→(111);在低的灯丝温度(≈1450℃)和低的衬底温度(≈235℃)条件下,获得了晶粒横向尺寸大于1μm、垂直尺寸大于5μm的均匀致密的多晶硅薄膜。     

常压化学气相沉积法制备氮化钛薄膜结构和节能性能研究

在普通玻璃基板上利用常压化学气相沉积法在580℃条件下制备得到了氮化钛薄膜。对薄膜的结晶性能、断面形貌、方块电阻以及光学透过率和反射率进行了研究。随着沉积时间的增长,薄膜由单层结构变为一种特殊的双层结构,这种双层结构的形成是沉积过程中气相成核机制引起的。光谱结果显示制备得到的薄膜具备一定的阳光控制性能。然而,双层薄膜的红外反射率随沉积时间的增长迅速降低,影响了其阳光控制性能。     

化学气相沉积法制备ZnS块材料的相结合

用敢相沉积法制备了红外晶体ＺｎＳ块材料；分别用ＸＲＤ和ＴＥＭ分析了所沉积ＺｎＳ的相结构，并用ＩＲ测试了其红外透过率，结果表明：在沉积温度为５５０－７００℃，Ｈ２Ｓ／Ｚｎ摩尔流量比为０．５－２０的条件下所沉积ＺｎＳ的相结构主要为闪锌矿结构；随着沉积温度的升高和Ｈ２Ｓ／Ｚｎ摩尔流量比的增大，ＺｎＳ中有纤锌矿结构出现且其含量增多，导致了ＺｎＳ红外透过率的降低。     

石墨烯的化学气相沉积法制备

化学气相沉积(CVD)法是近年来发展起来的制备石墨烯的新方法,具有产物质量高、生长面积大等优点,逐渐成为制备高质量石墨烯的主要方法.通过简要分析石墨烯的几种主要制备方法(胶带剥离法、化学剥离法、SiC外延生长法和CVD方法)的原理和特点,重点从结构控制、质量提高以及大面积生长等方面评述了CVD法制备石墨烯及其转移技术的研究进展,并展望了未来CVD法制备石墨烯的可能发展方向,如大面积单晶石墨烯、石墨烯带和石墨烯宏观体的制备与无损转移等.     

具有立方晶核ZnSe四足纳米晶的制备与表征(英文)

纳米材料的本征性质与其结构密切相关,在纳米尺度操控材料并表征其结构是纳米科学与技术的关键.采用热蒸发法制备了一种四足结构ZnSe纳米晶,通过高分辨透射电子显微镜对这种四足ZnSe纳米晶的晶体结构进行了表征.该ZnSe纳米晶由一个四面体的立方晶核和四个沿[001]方向生长的六方相分枝构成.本研究对这种ZnSe纳米晶的形貌和结构进行了讨论,证明了在ZnSe纳米晶内两种晶相的共存.根据ZnSe的结晶学特性和晶相的温度稳定性,解释了这种四足结构纳米晶的生长机制:ZnSe的四面体立方晶核在高温区域形成后,ZnSe蒸汽在低温区继续沉积在晶核上形成四个六方相的分支足,最终形成了具有立方晶核的ZnSe四足纳米晶.     

High pressure effect on MoS<Subscript>2</Subscript> and MoSe<Subscript>2</Subscript> single crystals grown by CVT method

Single crystals of MoS₂ and MoSe₂ were grown by chemical vapour transport method using iodine as a transporting agent and characterized by optical microscopy, energy dispersive analysis (EDAX), X-ray powder diffraction (XRD) and Hall mobility at room temperature. The variation of electrical resistance under pressure was monitored in a Bridgman anvil set-up up to 6.5 GPa to identify occurrence of any structural transition. MoS₂ and MoSe₂ do not undergo any structural transitions under pressure.     

Optical characterization of Er-doped ZnSe for scintillation applications

The effect of Er-doping of ZnSe crystals on luminescence and structural properties was investigated using low-temperature photoluminescence, X-ray luminescence, Raman and IR spectroscopies. It was found that Er dopant atoms with the concentration in the solid phase of about 10⁻³ wt.% lead to a substantial disordering of initial crystalline structure. The mentioned processes manifest in substantial decrease of the amplitudes of corresponding vibrational modes and increase of their FWHM in first-order Raman spectra of Er-doped ZnSe crystals. Also, Er-doping stimulates an appearance of additional absorbance bands in IR transmittance spectra. However, Er-doping leads to substantial increase of the efficiency of photoluminescence and X-ray luminescence that is very important for scintillation application. In this case, the luminescence is mainly caused by recombination via defect centers which contain Er atoms incorporated in the ZnSe lattice in different electronic configurations.     

Spectroscopic evidence and control of compensating native defects in doped ZnSe

Electron paramagnetic resonance spectroscopy combined with photoexcitation is used to identify and characterise the defects responsible for the compensation in iodine or aluminium doped ZnSe bulk crystals. The principal g-values of the Al_ZnV_Zn complex are reported for the first time. The acceptor levels of both A-centres observed are determined at 0.50 and 0.54 eV above the valence band edge for I_SeV_Zn and Al_ZnV_Zn, respectively. Annealing of these samples in Zn vapour is shown to be suitable for reproducible adjustments of the electron concentration at room temperature up to a few 10¹⁸ cm⁻³. The tight coupling of these vapour phase equilibrations with the electrical and spectroscopic analysis allows to propose a simple defect-chemical model.     

水合肼还原法制备球形钴粉

以水合肼为还原剂,在碱性条件下室温还原六水合硝酸钴(Co(NO3)2·6H2O)制备钴粉.探究了NaOH加入量对钴粉晶体结构的影响,以及NaOH加入量和3种不同的钴离子溶剂对形貌的影响.结果表明:在实验浓度范围内,所制备钴粉样品中fcc相的百分含量随着NaOH量的增加而呈不断增大的趋势;NaOH量较低时,钴粉为表面光滑的球形颗粒,随着NaOH量的增加,颗粒偏离球形,表面变粗糙,而当NaOH量较大时,颗粒形状变得不规则,且尺寸变小;以乙二醇为钴离子溶剂可制得表面光滑的完整球形钴粉颗粒.     

Graphene Single Crystals: Size and Morphology Engineering

Recently developed chemical vapor deposition (CVD) is considered as an effective way to large‐area and high‐quality graphene preparation due to its ultra‐low cost, high controllability, and high scalability. However, CVD‐grown graphene film is polycrystalline, and composed of numerous grains separated by grain boundaries, which are detrimental to graphene‐based electronics. Intensive investigations have been inspired on the controlled growth of graphene single crystals with the absence of intrinsic defects. As the two most concerned parameters, the size and morphology serve critical roles in affecting properties and understanding the growth mechanism of graphene crystals. Therefore, a precise tuning of the size and morphology will be of great significance in scale‐up graphene production and wide applications. Here, recent advances in the synthesis of graphene single crystals on both metals and dielectric substrates by the CVD method are discussed. The review mainly covers the size and morphology engineering of graphene single crystals. Furthermore, recent progress in the growth mechanism and device applications of graphene single crystals are presented. Finally, the opportunities and challenges are discussed.     

钨酸铅(PbWO4)闪烁晶体的结构研究进展

介绍近年来在钨酸铅闪烁晶体结构研究方面所取得的进展,表明钨酸铅晶体结构具有结构多型性和非化学计量配比的特征,说明了晶体结构这一因素在钨酸铅晶体研究中的重要性．     

Growth Mechanism of Different Morphologies of ZnO Crystals Prepared by Hydrothermal Method

Different morphologies of zinc oxide(ZnO),including microrods,hexagonal pyramid-like rods and flower-like rod aggregates,had been synthesized,respectively,on glass substrates by controlling the reaction conditions(such as precursor concentration,reaction time and pH value) of hydrothermal method.The morphologies of the as-obtained ZnO were observed with scanning electron microscopy and transmission electron microscopy.Also,the crystalline natures of different ZnO crystals were analyzed with X-ray diffraction.The possible growth mechanism of ZnO crystals with different morphologies was discussed.     

钨酸铅(PbWO4)闪烁晶体的结构研究进展

介绍近年来在钨酸铅闪烁晶体结构研究方面所取得的进展,表明钨酸铅晶体结构具有结构多型性和非化学计量配比的特征,说明了晶体结构这一因素在钨酸铅晶体研究中的重要性.