氢气对AlN薄膜择优取向的作用机制

采用脉冲反应磁控溅射方法在Si衬底上沉积了(100)和(002)择优取向的AlN薄膜,随着溅射功率的降低或氢气浓度的增加,放电电压下降,沉积粒子能量降低,薄膜由(002)取向逐渐向(100)取向转变.在溅射气氛中加入氢气后,薄膜中的氧含量降低,表面形貌与表面粗糙度均随着择优取向的改变发生变化.溅射功率及氢气浓度对AlN薄膜择优取向的影响规律表明,氢气主要是通过降低沉积粒子的能量和在衬底表面产生吸附两种作用方式来影响AlN薄膜的择优取向.     

射频磁控溅射不锈钢衬底AlN薄膜的制备与特性研究

利用正交实验设计方法,采用射频磁控溅射法在不锈钢衬底上制备了AlN薄膜,并利用XRD、激光拉曼光谱、荧光光谱等技术对AlN薄膜的结构及发光特性进行了表征.通过实验数据分析,得出如下结论:利用射频磁控溅射法在不锈钢衬底上制备的纤锌矿结构AlN薄膜,在所有参数下,(100)面最易生长;在溅射功率为300～400 W、衬底温度为100～200 ℃、氮气流量百分比为30;、溅射时间为1 h时,制备出的AlN薄膜结晶状况较好.制备出的AlN薄膜没有明显的拉曼峰,但不锈钢衬底不仅有拉曼峰,而巨在紫外区有很强的荧光发射峰.在不锈钢上镀膜后,拉曼峰的强度有所变化并巨伴随着频移.     

衬底温度对含硅量子点的SiCx薄膜结构及其光学特性的影响

采用磁控共溅射沉积法,以Si靶和SiC靶为靶材,单晶Si(100)和石英为衬底,在不同衬底温度下沉积了富硅SiCx薄膜.在氮气氛下于1100 ℃退火,得到包含硅量子点的SiCx薄膜.采用傅立叶变换红外吸收光谱、拉曼光谱、掠入射X射线衍射和吸收谱对退火后的SiCx薄膜进行了表征.结果表明:当衬底温度从室温(25℃)升至300℃时,薄膜的晶化率增至71.3;,硅量子点尺寸增至8.9 nm,而光学带隙则减至2.42 eV;随着衬底温度进一步升高,薄膜的晶化率降至63.1;,硅量子点尺寸减小至7.3 nm,而光学带隙却增加至2.57 eV;当衬底温度从室温(25℃)升至400℃时,薄膜的吸收系数呈先增大后减小趋势.在本实验条件下,最佳衬底温度为300℃.     

双靶反应磁控溅射共沉积AlN薄膜粘结性能研究

采用单、双靶反应磁控溅射法分别在45钢、GCr15钢、硅(100)和钼衬底上制备了AlN薄膜.X射线衍射和电子显微分析表明,双靶反应磁控溅射沉积的AlN薄膜具有高致密度和低残余应力,同时采用划痕法和压痕法等对AlN薄膜的粘结强度进行测试, 结果表明:双靶反应磁控溅射共沉积AlN薄膜的粘结强度明显比单靶沉积的薄膜高,划痕临界载荷提高0.5～2倍.不同衬底上沉积的AlN薄膜粘结强度存在很大的差别,以钼衬底上沉积的薄膜粘结强度最高,划痕法测得的临界载荷高达64 N;GCr15衬底上AlN薄膜摩擦试验表明,AlN薄膜能明显起到减磨作用.     

Si和6H-SiC衬底上β-FeSi2薄膜的制备

以6H-SiC (0001) Si面和Si(100)为衬底,采用磁控溅射Fe-Si合金靶和Si靶两靶共溅射的方法,并经过后续的快速退火成功制备了β-FeSi2薄膜.通过X射线衍射(XRD)、拉曼(RAMAN)和电子扫描电镜(SEM)研究了不同衬底对薄膜生长过程的影响.结果表明:与Si衬底不同,6H-SiC为衬底所生长的FeSix薄膜与衬底之间很难产生相互扩散,导致薄膜中的Si原子主要来源于靶材.同时分析不同退火温度对6H-SiC衬底和Si衬底上的FeSix薄膜的影响,并相比较.结果表明:不同衬底Si(100)和6H-SiC (0001) Si面所生长的薄膜经900℃退火时皆完全转化为多晶β-FeSi2相,其择优取向皆为(220)/(202),且随温度从500℃到900℃的不断上升,(220)/(202)衍射峰的强度增强,半高宽变小,得到900℃下的半高宽为0.33°.     

热丝CVD法在单晶硅衬底上低温外延生长Si和Ge薄膜的研究

采用热丝CVD法在单晶Si衬底上进行了Si和Ge 薄膜的低温外延生长,用XRD和Raman谱对其结构性能进行了分析.结果表明:在衬底温度200 ℃时,Si(111)单晶衬底上外延生长出了Raman峰位置为521.0 cm-1;X射线半峰宽(FWHM)为5.04 cm-1.结晶质量非常接近于体单晶的(111)取向的本征Si薄膜;在衬底温度为300 ℃时,在Si(100)单晶衬底上异质外延,得到了Raman峰位置为300.3 cm-1的Ge薄膜,Ge薄膜的晶体取向为Ge(220).研究表明热丝CVD是一种很好的低温外延薄膜的方法.     

退火温度对La3Ga5SiO14薄膜结构及表面形貌的影响

采用脉冲激光沉积技术在Si(100)衬底上制备了La3Ga5SiO14薄膜,并研究了不同的退火温度对薄膜结构和表面形貌的影响.衬底温度为室温时生长的薄膜经过800 ℃以上的高温退火后,由最初的无定形态转变为无规则取向的多晶结构.衬底温度为400 ℃时生长的薄膜经过800 ℃退火处理后呈现无序的多晶形态.当退火温度进一步升高至1000 ℃时,XRD图谱显示薄膜由最初的(220)和(300)两个结晶方向转变为以(200)和(400)为主要取向的多晶结构.表面形貌分析表明:衬底温度为400 ℃时,随着退火温度的升高,薄膜颗粒尺寸逐渐增大,表面无裂纹,而衬底温度为室温时生长的薄膜退火后则出现大量的裂缝、孔洞等缺陷.     

不同磁控溅射方式制备的C掺杂h-BN薄膜微观结构与导电性研究

采用中频双极脉冲(IFBP)和射频(RF)磁控溅射分别在(100)取向的单晶Si衬底上沉积C掺杂h-BN(h-BN:C)薄膜,随后在95;Ar+5;H2混合气氛中进行700℃退火处理,对其结构、化学组成、元素的化学价态、表面形貌以及导电性进行了分析研究.结果表明:两种溅射方法均成功在Si基片上制备出致密连续的h-BN:C薄膜,其电阻率可低至2.9×104～2.5×105Ω·cm.对比发现两种制备方法中IFBP磁控溅射具有较快沉积速率,制备出的h-BN:C薄膜结构更稳定,结晶性更好;而RF磁控溅射制备的h-BN:C薄膜经700℃退火处理后形成了层状结构.在溅射气氛中掺入一定量H2对提高h-BN:C薄膜稳定性极为重要,而沉积后的低温退火处理更可提高其结晶性和稳定性.     

磁控溅射参数对（Ba,Sr）TiO3薄膜择优取向生长的影响

采用磁控溅射法在Pt/Ti/SiO2/Si衬底上制备了(Ba,Sr)TiO3薄膜。基于薄膜的形核理论,研究了溅射气压、靶基距、衬底温度和溅射功率等溅射参数对(Ba,Sr)TiO3薄膜择优取向生长的影响。实验结果表明:磁控溅射中,较高衬底温度(600℃)有助于钙钛矿成相;通过改变磁控溅射参数,能得到(111)、(001)、(110)择优取向的薄膜。     

大气开放式MOCVD氧化镁薄膜的生长及表征

以2,4-乙酰丙酮化镁为前驱体,衬底温度为480℃,采用MOCVD工艺,分别在玻璃、氧化铝陶瓷、单晶Si(111)和Si(100)衬底上生长了取向生长的氧化镁薄膜。X射线衍射结果表明,无论是采用玻璃、氧化铝、单晶Si(111)和Si(100)衬底,氧化镁薄膜都是沿着(100)晶面取向生长。通过扫描电镜观察得到,在单晶Si(100)衬底上生长的氧化镁薄膜表面平整致密。模拟卢瑟福背散射结果显示,沉积时间超过70min时,界面处发生硅向氧化镁层少量扩散现象。     

CsI-LiCl共晶材料的坩埚下降法生长与闪烁性能研究

本文采用坩埚下降法,在真空密封的石英坩埚中成功生长出CsI-LiCl与CsI-LiCl:Na共晶闪烁体。通过扫描电子显微镜(SEM)观察晶体微结构表明该共晶中LiCl相与CsI相存在周期性的层状排列,CsI相的厚度在5 μm左右。共晶样品的X射线激发发射谱显示在CsI-LiCl和CsI-LiCl:Na共晶样品存在缺陷发光,在CsI-LiCl样品中还观察到了纯CsI的自陷激子(STE)发光。CsI-LiCl样品在α粒子激发下的多道能谱中观察到明显的全能峰,这一结果证明CsI-LiCl共晶可用于热中子探测的潜力。     

静电纺丝法制备CeO2微纳米纤维及其除氟性能

以聚丙烯腈(PAN)为载体,六水合硝酸铈[Ce(NO₃)₃·6H₂O]为原料,采用静电纺丝法制备了Ce(NO₃)₃/PAN纤维,在空气中热处理得到CeO₂微纳米纤维,通过XRD、BET和SEM对CeO₂微纳米纤维进行表征。采用静态吸附实验探讨了CeO₂微纳米纤维去除水溶液中氟离子的性能,考察了溶液pH值、初始氟离子浓度及共存阴离子等对吸附性能的影响。结果表明,pH=3时,CeO₂微纳米纤维对F^-的吸附性能最佳,CeO₂吸附量随着F^-浓度的增大呈上升趋势。CeO₂微纳米纤维对F^-的吸附等温线遵循Langmuir模型,二级动力学模型能很好地描述CeO₂微纳米纤维对F^-的吸附过程。CeO₂微纳米纤维的除氟性能优良,可为其实际应用提供理论参考。     

Triethyl ammonium salt of O,O′-bis(p-tolyl)dithiophosphate, [Et3NH]+[(4-MeC6H4O)2PS2]−

Triethyl ammonium Salt of O,O′-bis(p-tolyl)dithiophosphate and O,O′-bis(m-tolyl)dithiophosphate have been obtained by reaction of p- and m-cresol, respectively with P₂S₅ in toluene and have been characterized by elemental analysis, IR, ¹H and ³¹P NMR spectroscopy. The molecular structure of O,O′-bis(p-tolyl)dithiophosphate has been determined. Crystal data: [Et₃NH]⁺[(4-MeC₆H₄O)₂PS₂]⁻: Monoclinic, P2₁/c, a=15.2441(9) ?, b=10.415(2) ?, c=3.9726(9) ?, β=91.709(7)°, V=2217.5(1) ?⁻³, Z=4.Supplementary materials Additional material available from the Cambridge Crystallographic Data Centre (CCDC no. 600927 for [Et₃NH]⁺[(4-MeC₆H₄O)₂PS₂]⁻ comprises the final atomic coordinates for all atoms, thermal parameters, and a complete listing of bond distances and angles. Copies of this information may be obtained free of charge on application to The Director, 12 Union Road, Cambridge CB2 2EZ, UK (fax: +44-1223-336033; email: deposit@ccdc.cam.ac.uk or www:http://www.ccdc.cam.ac.uk).     

Crystal structure of Zn4Na(OH)6SO4Cl·6H2O

The structure of Zn₄Na(OH)₆SO₄Cl·6H₂O, a secondary mineral from Hettstedt, Germany, was determined by single-crystal X-ray diffraction. The crystals are hexagonal,a=8.413(8),c=13.095(24) Å, space group $P\bar 3$ , Z=2. The structure was refined to R=0.0554 and R_w=0.0903 for 970 reflections with I≥3σ(I). The structure can be described as zinc hydroxide layers perpendicular toc, from which sulfates and chlorides extend. The layers are held together by a system of hydrogen bonds involving hexaaquo Na⁺ ions which occupy the interlayer space.     

X-ray analysis of sideroxol from <Emphasis Type="Italic">Sideritis leptoclada</Emphasis>

Sideroxol (1), a kaurane diterpene which has the ent-7α,18-dihydroxy-15β,16β-epoxykaurane structure (MW = 320.47, C₂₀H₃₂O₃) was obtained from the acetone extract of Sideritis leptoclada plant as well as from some other Sideritis species. It crystallizes in the orthorhombic space group P2₁, 2₁, 2₁ with a = 10.967(3), b = 24.555(5), c = 6.372(4) Å, Dc = 1.240 g cm⁻³, Z = 4, and refines to R = 0.065 for 721 independent reflections. The skeleton consists of three fused six-membered rings and a five-membered ring with fused epoxide. The six membered rings exhibited slightly distorted chair conformation. In addition to sideroxol, two kaurane and five kaurene diterpenes were isolated from the hexane and acetone extracts of the studied plant.     

Photoluminescence characteristics of Mg- and Si-doped GaN thin films grown by MOCVD technique

We have studied the optical, structural and surface morphology of doped and undoped GaN thin films. The p- and n-type thin films have been successfully prepared by low-pressure MOCVD technique by doping with Mg and Si, respectively. The different carrier concentrations were obtained in the GaN thin films by varying dopant concentrations. Photoluminescence (PL) studies were carried to find the defect levels in the doped and undoped GaN thin films at low temperature. In the undoped GaN thin films, a low intensity and broad yellow band peak was observed. The donor–acceptor pair (DAP) emission and its phonon replicas were observed in both the Si or Mg lightly doped GaN thin films. The dominance of the blue and the yellow emissions increased in the PL spectra, as the carrier concentration was increased. The XRD and SEM analyses were employed to study the structural and surface morphology of the films, respectively. Both the doped and the undoped films exhibited hexagonal structure and polycrystalline nature. Mg-doped GaN thin films showed columnar structure whereas Si-doped films exhibited spherical shape grains.     

New zeotype borophosphates with chiral tetrahedral topology: (H)0.5M1.25(H2O)1.5[BP2O8]·H2O (M = Co(II) and Mn(II))

Two new isostructural open‐framework zeotype transition metal borophosphate compounds, (H)_0.5M_1.25(H₂O)_1.5[BP₂O₈]·H₂O (M = Co(II) and Mn(II)) were synthesized by mild hydrothermal method. The structure of compounds were characterized by single‐crystal X‐ray diffraction which have ordered, alternating, vertex‐sharing BO₄, PO₄, and (MO₄)OM(H₂O)₂ groups with hexagonal, P 6₁ 2 2 (No 178) space group and unit cell parameters for Co a = 9.4960(6) Å, c = 15.6230(13) Å, for Mn a = 9.6547(12) Å, c = 15.791(3) Å, Z = 1 for both of them. TGA/DTA analysis, IR spectroscopy were used for characterization. Magnetic susceptibility measurements for both of the compound indicate strong antiferromagnetic interaction between metal centers. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and Crystal Structure of 5-[2-(6-bromonaphthalenyloxymethyl)]-3-(4-morpholinomethyl)-1,3,4-oxadiazole-2(3<Emphasis Type="Italic">H</Emphasis>)-thione

Abstract  The title compound, C₁₈H₁₈BrN₃O₃S, a derivative of 1,3,4-oxadiazole, crystallizes in the triclinic space group P-1 with unit cell parameters a = 6.8731(3), b = 8.9994(4), c = 15.7099(6) ?, α = 92.779(3)°, β = 130.575(3)°, γ = 107.868(4)°, Z = 2. The dihedral angle between the mean planes of the planar naphthyl and morpholine (chair) rings with the planar oxadiazol ring is 50.1(8) and 76.8(6)°, respectively. The planar naphthyl ring is twisted 52.2(5)° with the mean plane of the morpholine ring. A group of four intermolecular close contacts are observed between a bromine atom and hydrogen atoms from the closely packed naphthyl, morpholine and oxy–methyl groups in the unit cell. These molecular interactions in concert with an additional series of π–π stacking interactions that occur between the center of gravity of the two 6-membered rings of the naphthalene group influence the twist angles of each of these three groups. A MOPAC AM1 calculation of the conformation energy of the crystal structure [226.0128(9) kcal] compared to that of the minimum energy structure after geometry optimization [29.9744(1) kcal] reveals a significantly reduced value. The twist angles of the three groups above also change after the AM1 calculation giving support to the influence of both intermolecular C–H···Br short-range interactions and Cg π–π stacking interactions on these angles which therefore play a role in stabilizing crystal packing. Graphical Abstract  Crystal structure of 5-{[(6-bromonaphthalen-2-yl)oxy]methyl}-3-(morpholin-4-ylmethyl)-1,3,4-oxadiazole-2(3H)-thione, C₁₈H₁₈BrN₃O₃S, is reported and its geometric and packing parameters described and compared to a MOPAC computational calculation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Solubility of Ag2O into the Na2O–B2O3–Al2O3 system

The solubility of Ag₂O was measured for the Na₂O–B₂O₃ and Na₂O–B₂O₃–Al₂O₃ system with the rotating crucible method and static method, respectively, under air atmosphere at temperatures ranging from 1273 to 1423 K. The contamination of melts from crucibles could be avoided by the rotating crucible method, with which it became possible to measure the solubility of Ag₂O for the Na₂O–B₂O₃ system above the melting point of Ag for the first time. It was found that the addition of Na₂O decreases the solubility of Ag₂O while the addition of Al₂O₃ had little effect on the solubility. The effect of Na₂O and Al₂O₃ on the solubility of Ag₂O is expressed by interaction coefficients and is analyzed in terms of the basicity of melts. The solubility of Ag₂O in Na₂O–B₂O₃–Al₂O₃ melts increased with increased temperature. This phenomena was explained by a small enthalpy change in oxidation of silver.     

Crystal structure of irisolidone from the flowers of Pueraia lobata

Irisolidone (5,7-dihydroxy-6,4′-dimethoxyisoflavone) was isolated from the flowers of Pueraia lobata and its crystal structure was examined by X-ray single crystal diffraction. The crystal structure of irisolidone is monoclinic, space group P2₁/c with a = 15.491(9) ?, b = 7.895(4) ?, c = 13.321(7) ?, β = 110.546(9)° and Z = 4. Hydrogen bonding and aromatic π–π stacking assemble the title compound into a three-dimensional networking structure.