薄膜厚度对MOCVD法沉积ZnO透明导电薄膜的影响

本文研究了薄膜厚度对MOCVD技术制备未掺杂ZnO薄膜的微观结构和电学特性影响.XRD和SEM的研究结果表明,随着薄膜厚度的增加,ZnO薄膜(110)峰趋于择优取向,且晶粒逐渐长大,薄膜从球状和细长棒状演变为具有类金字塔绒面结构特征的ZnO薄膜;Hall测量表明,较厚的ZnO薄膜有助于提高薄膜电学特性,可归于晶粒长大和晶体质量提高.40min沉积时间(膜厚为1250nm)制备出的ZnO薄膜具有明显绒面结构,其晶粒尺寸为300～500nm,电阻率为7.9×10-3Ω·cm,迁移率为26.8cm2/Vs.     

Nb掺杂ZnO透明导电薄膜的结构以及光电性能研究

采用直流磁控溅射法在玻璃衬底上制备了高质量的Nb掺杂ZnO( NZO)透明导电薄膜.为了研究薄膜厚度对薄膜性质的影响,制备了五个厚度分别为239 nm,355 nm,489 nm,575 nm和679 nm的样品.XRD结果表明,ZnO∶ Nb薄膜是具有六角纤锌矿结构的多晶薄膜,并且具有垂直于衬底的c轴择优取向.随着膜厚的增加,薄膜的结晶质量明显提高.当厚度从239 nm增加到489 nm时,平均晶粒尺寸从19.7 nm增加到24.7 nm,薄膜的电阻率持续减小;当厚度进一步增加时,晶粒尺寸略有减小,电阻率有所增加.本实验获得的最低电阻率为4.896×10-4Ω·cm.随膜厚的增加,光学带隙先增大后减小.所有薄膜在可见光区域的平均透过率均超过88.3;.     

膜厚对Zr,Al共掺杂ZnO透明导电薄膜结构和光电性能的影响

采用直流磁控溅射法在玻璃衬底上制备出Zr,Al共掺杂ZnO(AZZO)透明导电薄膜.用XRD和SEM分析和观察了薄膜样品的组织结构和表面形貌.研究表明:制备的AZZO透明导电薄膜为六角纤锌矿结构的多晶薄膜,且具有c轴择优取向.另外还研究了薄膜的结构、光学和电学性质随薄膜厚度的变化关系.当薄膜厚度为843 nm时,电阻率具有最小值1.18×10~(-3) Ω·cm,在可见光区(500～800 nm)平均透过率超过93;.     

Sn掺杂对ZnO薄膜结构和光电性能的影响

采用溶胶-凝胶浸渍提拉法在玻璃衬底上制备了Sn掺杂ZnO(SZO)薄膜。通过X射线衍射(XRD)和扫描电镜(SEM)研究了Sn掺杂对薄膜表面形貌和微结构的影响。XRD结果表明,所有ZnO薄膜样品都存在(002)择优取向。SEM结果表明随着掺杂浓度的增加,薄膜表面由颗粒向纳米棒转变。电学结果显示掺杂浓度为3at%时,电学性能最好,最低电阻率为6.9×10-2Ω.cm。室温光致发光谱(PL)显示所有的SZO薄膜样品在(325 nm光激发下)380 nm和398 nm两处都有发光峰,随着掺杂浓度的增大,398 nm处的发光强度先增大后减小,然后再增大;380nm处的发光强度始终增大,这些现象与薄膜的表面结构的变化有关。     

B掺杂对平面结构MOCVD-ZnO薄膜性能的影响

本文研究了B2H6掺杂流量(B掺杂)对平面结构MOCVD-ZnO薄膜的微观结构和光电性能影响.XRD、SEM和AFM测试的研究结果表明,玻璃衬底上制备的ZnO薄膜具有(002)峰择优取向的平面结构,B掺杂使薄膜的球状晶粒尺寸变小,10 sccm流量时晶粒尺寸为～15 nm.ZnO:B薄膜的最小电阻率为5.7×10-3Ω·cm.生长的ZnO薄膜(厚度d=1150 nm)在400～900 nm范围的透过率为82;～97;,且随着B2H6掺杂流量增大,光学吸收边呈现蓝移(即光学带隙Eg展宽)现象.     

薄膜厚度对ZnO:Y薄膜结构及光电特性影响

室温下采用射频磁控溅射法在玻璃衬底上制备出了具有良好附着性、低电阻率和高透过率的新型ZnO∶Y(ZnO掺杂Y2O3,简称ZnO∶Y)透明导电薄膜。研究了薄膜厚度对ZnO∶Y薄膜结构、光电特性的影响。结果表明:不同厚度的ZnO∶Y薄膜均为多晶薄膜,具有ZnO六角纤锌矿结构,最佳取向为(002)方向。随薄膜厚度增加,其电阻率减小,当薄膜厚度增至800 nm时,其电阻率为8.36×10-4Ω.cm,迁移率为15.3 cm2.V-1.s-1,载流子浓度为4.88×1020cm-3。不同厚度的薄膜在可见光范围内平均透过率均为90%以上,当薄膜厚度从200 nm增加到800 nm时,薄膜禁带宽度从3.68 eV减小到3.61 eV。     

化学浴法制备CdS薄膜及其光电性能研究

本文用氯化镉、氯化铵、硫脲和氨水的溶液体系采用化学浴沉积法合成CdS薄膜,制备出均匀、致密的CdS薄膜,通过XRD、SEM、EDS、紫外可见吸收光谱等表征手段研究了CdS薄膜的晶体结构,表面形貌,元素比例和光电性能.发现在不同水浴温度下都成功制备了CdS薄膜,其中75℃制备的CdS薄膜最为均匀致密且其XRD衍射峰强度最强,光吸收边在500 nm附近,禁带宽度大约为2.52 eV.这些CdS薄膜的光电响应大,暗态及光照下的电导率分别为1×10-4S·cm-1和1.04×10-2 S · cm-1.用它们制备的CdS/CZTS异质结太阳电池具有明显的光伏效应.     

Al-H共掺杂ZnO薄膜的形貌及光致发光性能研究

在不同衬底温度条件下采用RF磁控溅射法在石英玻璃上沉积Al-H共掺杂ZnO薄膜.对所有样品进行晶体结构、表面形貌、电学、光学以及室温光致发光性能分析.结果表明:随着衬底温度的升高,ZnO薄膜的结晶度增加,晶粒增大,薄膜致密度增加;薄膜表面起伏变化减小;同时,电阻率最低达到7.58×10-4Ω·cm,透过率保持在75;左右.所有ZnO薄膜样品都以本征发光为主,Al-H共掺杂在一定程度降低ZnO薄膜缺陷发光的强度;随着衬底温度的升高,ZnO薄膜的本征发光强度明显增大;同时在能量为3.45 eV附近观察到了一个紫外发光峰.     

Fe、Ni共掺杂ZnO薄膜的溶胶-凝胶法制备及性能研究

采用溶胶-凝胶法在玻璃基片上旋涂生长了ZnO、Fe, Ni单掺杂及(Fe,Ni)共掺杂ZnO薄膜.产物的显微照片及XRD图谱结果表明, 该方法所制备的ZnO薄膜表面均匀致密,都存在(002)择优取向,具有六角纤锌矿结构,晶粒尺寸平均在13 nm 左右,振动样品磁强计(VSM)测试结果显示掺杂ZnO薄膜均存在室温铁磁性.光致发光(PL)测量表明所有样品薄膜的PL谱主要由较强的紫外发光峰(394 nm)、蓝光峰(420 nm)、绿光峰(480 nm)组成.Fe、Ni单掺杂和共掺杂并不改变ZnO薄膜的发光峰位置,但掺杂后该紫外发光峰减弱,420 nm处的蓝光峰增强.     

N掺杂MgxZn1-xO薄膜结构和光学性质研究

采用溶胶-凝胶法在玻璃衬底上制备了N掺杂MgxZn1-xO薄膜.通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射光谱、光致发光(PL)谱对N掺杂MgxZn1-xO薄膜样品的晶体结构、表面形貌和光学性能进行了研究.XRD结果表明所有样品均形成了MgZnO合金薄膜,没有观察到其它氧化物的衍射峰.样品的结晶质量越差,样品的表面形貌越不规则,但样品在可见光的透射率越强,甚至达到了95;.样品的禁带宽度随Mg含量的增加而增加,随N含量的增加而减小.所有样品的光致发光谱均观察到强的400 nm发光和弱的可见发光.400 nm的发光强度随Mg含量的增加而减弱,随N含量的增加而增强,认为薄膜在400 nm的发光来源ZnO的激子复合.     

Modelling of mechanism of agglomeration of KCl crystallization

The article presents an analysis into agglomeration during KCl vacuum crystallization. The theoretical and experimental investigations into the mechanism of agglomeration during mass crystallization result in an extension of the growth phenomena within the known model equations. The basis for this is essentially constituted by the collision model concepts of the theory of floculation in disperse systems. The parameters derived from the microprocess analysis (energy dissipation, content of solids, growth rate of individual grains) lead to model equations which are confirmed by laboratory and test trials.     

Relationship of Morphological Types of Dynamic Forms of Crystals

Crystallography Reports - The relationship of morphological spectra (sets of data on the morphological types of real polyhedral crystals and their probabilities under current physicochemical...     

Development of Pauling's concepts of geometric characteristics of atoms

The evolution of the geometric characteristics introduced by Pauling and their dependence on the specific features of the structure and chemical bonds have been considered. The values of the covalent and van der Waals radii are given as well as their relationships and mutual transitions.     

A review of measurement of thermophysical properties of silicon melt

Measurements of thermophysical properties of Si melt and supplementary study of X-ray scattering/diffraction by the authors' group were reviewed. The values obtained differed variously from those of literature. Density was 2–3% larger, surface tension 20–30% smaller, viscosity up to 40% larger, electrical conductivity 8% smaller, spectral emissivity more or less in good agreement with literature values, and thermal diffusivity a few percent larger. An anomalous density jump was found near the melting point. Surface tension and viscosity also showed anomaly. A strange time-dependent change of density was observed over 3 h after melting. X-ray analyses suggested a slight change in local atom ordering, but showed no sign of cluster formation. An addition of 0.1 at% gallium caused the density jump to disappear, while that of boron caused no change. An EXAFS study of the former melt indicated a strong interaction between Ga and Si atoms as if molecules of GaSi₃ existed. The implications of the measured properties are a possibility of soft-turbulence in an Si melt in a relatively large crucible, a more complicated manner of intake of oxygen depleted molten Si from the free surface region to underneath the growing crystal, and a relaxation of the melt after melting arising from trapped gas species.     

Generation of crystal structures of heteromolecular compounds by the method of discrete modeling of packings

Within the method of discrete modeling of packings, an algorithm of generation of possible crystal structures of heteromolecular compounds containing two or three molecules in the primitive unit cell, one of which has an arbitrary shape and the other (two others) has a shape close to spherical, is proposed. On the basis of this algorithm, a software package for personal computers is developed. This package has been approved for a number of compounds, investigated previously by X-ray diffraction analysis. The results of generation of structures of five compounds—four organic salts (with one or two spherical anions) and one solvate—are represented.     

Velocities of Disappearance and Lifetime of Faces of Growing Crystals

The formulae for absolute R_disap and relative R velocities of disappearance and lifetime τ of faces of growing crystals have been derived for stationary growth. It was shown that the quantities are determined by the relative growth velocity R_A/R_critA of the vanishing face A with respect to the critical growth velocity R_critA and by the geometry of a crystal expressed by the trigonometric functions of interfacial angles β and γ formed between face A and the adjacent faces. R increases and τ decreases with the increase in R_A/R_critA to certain limiting values. The calculations have been verified and illustrated by the experimental results for triclinic potassium bichromate (KBC) crystals. Results enable ones to predict values of velocities of disappearance and lifetimes of undesirable, supplementary faces of any real crystal.     

Dependence of the parameters of equations of viscous flow on chemical composition of silicate melts

The temperature dependence of viscosity of silicate melts is discussed in the framework of the Avramov–Milchev (AM) equation. The composition is described by means of two parameters: the molar fraction, x, and the “lubricant fraction”, l. The molar fraction is the sum of the molar parts x_i of all oxides dissolved in SiO₂, the molar fraction of the latter being 1 ? x. It is shown that, with sufficient precision, two of the parameters of the AM equation can be presented as unique functions of the molar fraction. On the other hand, x is not sufficient to determine properly the reference temperature T_r , at which viscosity is η_r = 10¹³ [dPa.s]. Therefore, additional parameter, “lubricant fraction” l, is introduced. For each of the components, l_i is a product of molar part x_i and a specific dimensionless coefficient 0 ≤ k_i ≤ 1 accounting for the specific contribution of this component to the increased mobility of the system. It is demonstrated that, for l > 0, the reference temperature is related to the “lubricant fraction” l through the reference temperature T_r,SiO2 of pure SiO₂.     

Comparative analysis of two methods of calculation of the orientation of domain walls in ferroelastics

Two types of domain-wall equations are analyzed: the equations derived by the Sapriel method and the equations obtained by interface matching of the thermal-expansion tensor. It is shown that, for W-type domain walls, these methods yield the same equations. For W′-type domain walls, the equations obtained by different methods coincide for proper ferroelastics and differ for improper ferroelastics.     

Mechanism of spatial ordering of dislocations during plastic deformation of crystals

Mechanisms of spatial ordering of dislocations during plastic deformation of crystals are considered. The system of evolution equations, which take into account the effects of elastic and correlated interactions of screw dislocations, is derived. The study is performed with due regard for the dynamics of spatial fluctuations of the dislocation density.