湿法腐蚀工艺研究碳化硅晶体缺陷表面形貌

采用湿法腐蚀工艺,对PVT法生长的碳化硅单晶缺陷进行了研究.利用熔融态KOH和K2CO8作为腐蚀剂,通过分别改变腐蚀剂配比、腐蚀时间、腐蚀温度的方法,获得了良好的湿法腐蚀工艺参数.用CCD光学显微镜和SEM观察腐蚀以后的晶体表面形貌.结果表明,最佳腐蚀工艺参数为K2CO3:KOH=5 g:200 g,440 ℃/30 min.腐蚀以后(0001)Si表面可以清晰地观察到微管、基面位错、螺位错和刃位错.实验还发现晶片表面抛光质量会影响腐蚀后SiC表面的形貌.     

提拉法Ti:LiAlO2晶体的生长、缺陷及N2退火研究

本文采用提拉法成功地生长了钛掺杂浓度为0.1%原子分数的LiAlO2单晶体,借助光学显微镜,结合化学腐蚀法,对Ti:LiAlO2晶体(100)面空气退火前后的缺陷特征进行了研究,用AFM观测了(100)面晶片在不同温度下流动N2气氛退火过的表面形貌。结果表明:Ti:LiAlO2晶体(100)面的位错腐蚀坑是底面为平行四边形的锥形坑,位错密度约为5.0×104cm-2,900℃空气退火后晶片表面的位错腐蚀坑变大;N2退火能显著影响晶片的表面形貌,当退火温度为900℃时,晶片的均方根粗糙度(RMS)达到最低值。     

XPS研究N-Al共掺p型ZnO薄膜的传导特性

采用螺旋波等离子体辅助射频磁控溅射技术,在α-Al2 O3衬底上制备了N-Al共掺ZnO薄膜样品.Hall测量表明室温下ZnAlO∶N薄膜为n型传导,在O2等离子体气氛中550℃退火后变为p型.p型ZnO薄膜的载流子浓度为2.1×1016 cm-3,霍尔迁移率为5 cm2/V·s.用X射线光电子能谱仪(XPS)对退火前后的ZnO薄膜进行了各元素的化学态分析.XPS结果表明,ZnAlO∶N薄膜中存在两种与N元素有关的缺陷,N原子替代O位形成的(N)o和N分子替代O位形成的(N2)o.退火后ZnAlO∶N薄膜中(N2)o缺陷减少,(N)o缺陷浓度占优导致了薄膜传导类型转变.     

半绝缘磷化铟中与非化学配比有关的深能级缺陷

在不同的化学配比条件下制备了半绝缘磷化铟材料,其中包括配比和富铟熔体中的铁掺杂以及磷气氛和磷化铁气氛下高温退火非掺杂晶片.在这些半绝缘磷化铟材料中检测到了与非化学配比有关的深能级缺陷.通过对大量的原生掺铁和非掺退火半绝缘磷化铟材料中的缺陷的研究,发现原生深能级缺陷与材料的电学参数质量密切相关.迁移率低、热稳定性差的掺铁半绝缘磷化铟材料中有大量的能级位于0.1～0.4eV之间的缺陷.高温退火非掺磷化铟抑制了这些缺陷的产生,获得了迁移率高、均匀性好的高质量半绝缘材料.根据这些结果,我们提出了一种通过控制化学配比制备高质量半绝缘磷化铟材料的方法.     

KBe2BO3F2和RbBe2BO3F2晶体中的孪晶缺陷

通过化学腐蚀和偏光显微镜,对KBe2BO3F2(KBBF)和RbBe2BO3F2 (RBBF)晶体中存在的一种条状孪晶缺陷进行了研究,观察了孪晶习性,探讨了其孪晶律,并结合晶体生长情况对该孪晶的形成原因进行了分析.     

GaSb/GaAs异质结热光伏电池材料的MBE生长

利用分子束外延方法(MBE)在GaAs (001)衬底上外延生长了GaSb薄膜,并对GaSb薄膜进行了高温退火研究,利用高分辨透射电子显微镜(HRTEM)、原子力显微镜(AFM)、Hall效应(Hall Effect)和低温光荧光谱(LTPL)等手段对薄膜的晶体质量、电学性质和光学性质进行了研究.发现直接生长的GaSb膜表面平整,空穴迁移率较高.研究发现30 s、650℃的快速热退火可消除位错等缺陷,显著提高GaSb薄膜的光学质量.     

重掺硅衬底片的内吸除效应

本文研究了重掺p型(B)和重掺n型(P、As、Sb)硅单晶的内吸除效应.发现在本实验条件下,经过改进的内吸杂(IG)处理后,不同掺杂剂的重掺硅单晶片都出现了氧沉淀增强现象,但不同掺杂剂的重掺硅单晶中氧沉淀形态不同.且发现砷增强了硅片近表层区氧的外扩散.在相同的热处理条件下,不同掺杂剂的重掺硅清洁区宽度不同,重掺硼硅片的清洁区最窄,重掺砷的最宽.     

定拉速生长对φ300 mm直拉硅单晶生长影响分析

作为集成电路制备的衬底材料,对硅单晶的均匀性以及微缺陷的尺寸、密度要求极高.传统直拉法生长硅单晶过程中,通过拉速变化控制晶体直径,因此拉速始终处于波动状态.恒定拉速对晶体均匀性及缺陷密度、尺寸的影响研究较少.本研究实现了在35±0.7 mm/h的拉速范围内生长出直径300 mm硅单晶,对晶体片间和片内电阻率分布以及FPD缺陷分布进行了检测,结果显示,在更小拉速波动阶段,晶体的电阻率均匀性得到改善,FPD缺陷密度降低.     

单晶硅外延生长晶化硅薄膜的研究

采用P型单晶硅片为衬底,并经混合酸溶液腐蚀抛光、清洗后,利用射频磁控溅射镀膜系统在其表面制备非晶硅薄膜;再结合快速光热退火工艺,于N2气氛下480℃退火30 min,得到晶化硅薄膜;利用光学金相显微镜、XRD衍射仪和拉曼散射光谱(Raman)仪对单晶硅衬底和晶化硅薄膜进行结构和性能表征.研究了混合酸溶液对单晶硅表面腐蚀效果、籽晶诱导外延生长晶化硅薄膜的物相结构和薄膜带隙.结果表明:采用混合酸溶液腐蚀后得到表面平整、光滑的单晶硅衬底;非晶硅薄膜经过快速退火后受籽晶诱导生成晶化硅薄膜,其晶相沿单晶硅衬底取向择优生长;随着非晶硅薄膜厚度从80 nm增加到280 nm,晶化后硅薄膜的表面粗糙度逐渐减小,晶化率从90.0;逐渐降低到37.0;;晶粒尺寸从6.65 nm逐渐减小到1.71 nm;带隙从1.18 eV逐渐升高到1.52 eV.     

硅酸钇晶体的生长、腐蚀形貌和光谱性能研究

本文采用中频感应提拉法成功生长了未掺杂的Y2SiO5(YSO)晶体,经过定向、切割、抛光后得到样品.经过腐蚀后,利用大视场显微镜和扫描电镜在样品表面上观察到了菱形和四边形的位错蚀坑、小角晶界和包裹物等缺陷;测试了经过氢气、空气退火前后,辐照前后YSO晶体的透过谱,结果表明:YSO晶体的吸收边大约在202nm,氢气退火后在200～300nm波段透过率增加,空气退火后透过率显著降低;辐照后,氢气退火的样品在200～500nm波段透过率显著降低.     

Palladium(II) and platinum(II) tetrakisthiourea dichloride bis(7-hydroxy-5-methyl[1,2,4]triazolo[1,5a]pyrimidine) dihydrate solvates

The title compounds palladium(II) and platinum(II) tetrakisthiourea dichloride bis(7-hydroxy-5-methyl[1,2,4]triazolo[1,5a]pyrimidine (Hmtpo)) dihydrate solvates, have been synthesized by reacting thecis-[MCl₂(Hmtpo)₂] (where M=Pt(II), Pd(II)) complexes with an excess of thiourea (tu) and the structure of the palladium compound was solved by X-ray diffraction. Crystals of [Pd(tu)₄]Cl₂·2Hmtpo·2H₂O are triclinic with space groupP and unit cell dimensionsa=7.972(1),b=9.049(1),c=11.808(2)Å, =88.20(1), =75.15(1), =76.54(1)^o. The cation [Pd(tu)₄]²⁺ is centrosymmetric involving four sulfur thiourea atoms in a near square planar environment. The triazolopyrimidine molecules, chloride anions and water molecules do not take part in the metal center coordination but interact by hydrogen bonding between them and the thiourea moieties. A comparison between powder diffraction data of palladium(II) and platinum(II) compounds clearly indicates that both compounds are isomorphous.     

Structures of Bis(1-ethylbenzimidazol-2-yl)alkyl Copper(II) Dichlorides: An Unusual Cocrystallization

Abstract  Two structures containing pseudo-tetrahedral Cu(II)N₂Cl₂ coordination complexes are reported. The first molecular structure (A) of the compound, 1,1′bis(1-ethylbenzimidazol-2-yl)propane copper(II) dichloride (triEtBBIM)Cu(II)Cl₂, 1, is reported. The complex crystallized in the triclinic space group P-1 with a = 8.616(3) ?, b = 9.302(3) ?, c = 14.314(4) ?, α = 85.613(6)°, β = 85.170(6)°, γ = 66.117(6)° and V = 1044.1(5) ?³ with Z = 2. The second structure (B) contains 1 and (3,3′bis(1-ethylbenzimidazol-2-yl)pentane) copper(II) dichloride (tetEtBBIM)Cu(II)Cl₂, 2, both of which, cocrystallize in an equal molar ratio with a nitromethane solvate molecule. The complex crystallized in the monoclinic space group P2₁/c with a = 18.876(4) ?, b = 14.975(3) ?, c = 18.344(4) ?, β = 116.75(3)°, and V = 4630.3(16) ?³ with Z = 4. The cocrystallization of such discrete complexes has been coined a chemical Janus. Graphical Abstract  The title complexes contain pseudo-tetrahedral Cu(II)N₂Cl₂ coordination. One of the structures is the result of an unusual cocrystallization, in which two different discrete Cu(II) molecules cocrystallize in an equimolar ratio with a nitromethane solvate molecule.      

Crystal structure of bis(4-dimethylaminopyridinium) tribromocuprate(I) and bis(4-dimethylaminopyridinium) tetrabromocuprate(II)

The synthesis and crystal structures of two copper bromide salts of the 4-dimethylaminopyridinium (4DMAP⁺) cation are reported. The Cu(I) salt, (4DMAP)₂CuBr₃, crystallizes in the monoclinic space group C2/c, with a = 11.724(2), b = 11.055(3), c = 15.763(3) Å, = 107.64(3)°, and Z = 4. It contains isolated planar 4DMAP⁺ cations and trigonal planar CuBr₃ ^2– anions. Small distortions from idealized D _3h symmetry are observed for the anion. For the Cu(II) salt, (4DMAP)₂CuBr₄, a triclinic cell is observed with a = 8.2373(2), b = 9.2428(2), c = 14.4391(1) Å, = 93.760(1), = 94.576(1), = 105.249(1)°, and Z = 2. This compound contains discrete planar 4DMAP⁺ cations and flattened tetrahedral CuBr₄ ^2– anions. Small distortions are observed for ideal D _2d symmetry.     

The syntheses and crystal structures of two chromium(III) and molybdenum(III) coordination compounds with 4-ethylpyridine

The structures of trichlorotris(4-ethylpyridine)chromium(III), [CrCl₃(C₇H₉N)₃] (I), and trichlorotris(4-ethylpyridine)molybdenum(III), [MoCl₃(C₇H₉N)₃] (II), consist of neutral molecules where three 4-ethylpyridine and three chloro ligands coordinate to the metal with a meridional configuration. Compound I crystallizes in a trigonal space group P3₁ with a = 11.515(2) Å and c = 15.378(3) Å. Compound II crystallizes in a monoclinic space group C2/c with a = 24.200(3) Å, b = 18.089(3) Å, c = 22.6004(7) Å and = 106.7137(6)°.     

Magnetotransport In (TMTSF)2PF6 and (TMTSF)2C104 Under Pressure

We have shown from the magnetotransport that the Fermi surface of (TMTSF)₂PF₆ is effectively closed two-dimensionally and is compensated in the metallic state at low temperature. These results are inconsistent with a broad regime of one-dimensional superconducting fluctuations.

Independent electron theory is seen to be inadequate to explain either the Fermi surface or the threshold field for oscillations, thereby implying that correlation effects are still important in the metallic state. Finally, an anomaly has been observed in the magnetotransport of (TMTSF)₂C10₄ which is analogous to the threshold field in (TMTSF)₂PF₆.     

Synthesis and characterization of ternary L-histidine complexes. Crystal structure of (2,2′-dipyridyl)-(L-histidinato-N,N′,O)copper(II) perchlorate 1.5 hydrate

A series of ternary complexes of copper(II), cobalt(II) and zinc(II) with L-histidine, 1,10-phenanthroline, 2,2-dipyridyl or imidazole having perchlorate or acetate as counterions were synthesized and characterized by conventional methods and for [Cu(bipy)(L-hist)]ClO₄·1.5H₂O and X-ray crystal structure was determined. The crystals belong to the monoclinic space groupC2 witha=18.843(3),b=10.582(2),c=11.020(2), =115.20(10)°,Z=4,R=0.0535. The structure is consistent of [Cu(bipy)(L-hist)]⁺ cations, perchlorate ions and water molecules. The geometry around copper is trigonal bipyramidal with one N,N,O tridentate L-histidine molecule and one 2,2-dipyridyl ligand, the apical sites are occupied by the -amino nitrogen [Cu–N(71) 1.995(8)] and by N(11) of 2,2-dipyridyl [Cu–N(11) 1.983(7)], the equatorial plane is formed by the N(3) imidazole -nitrogen [Cu–N(3) 2.140(6)], O(82) carboxylic oxygen [Cu–O(82) 2.009(5)] and N(22) [Cu–N(22) 2.010(7)].     

Crystal structures of the cobalt(III), nickel(II), copper(II), and zinc(II) complexes of 2-thio-6-picoline N-oxide

Structures of the following compounds have been solved: tris(2-thio-6-picoline N-oxide)cobalt(III), [Co(6MOS)₃], orthorhombic, Pca2₁, a = 17.871(3), b = 14.061(2), c = 15.964(2) Å, V = 4011(1) ų, Z = 8, and = 1.193 mm^–1; bis (2-thio-6-picoline N-oxide)nickel(II), [Ni(6MOS)₂], orthorhombic, Pbca, a = 15.602(8), b = 13.606(4), c = 13.348(8) Å, V = 2833(4) ų, Z = 8, and = 1.655 mm^–1; bis(2-thio-6-picoline N-oxide)copper(II), [Cu(6MOS)₂], orthorhombic, Pbca, a = 13.914(5), b = 12.984(5), c = 15.663(6) Å, V = 2830(2) ų, Z = 8, and = 1.836 mm^–1; and bis(2-thio-6-picoline N-oxide)zinc(II), [Zn(6MOS)₂], triclinic, P – 1, a = 7.9737(8), b = 11.7786(9), c = 7.9206(8) Å, = 104.502(7), = 104.495(8), = 93.445(8)°, V = 691.3(1) ų, Z = 2, and = 2.106 mm^–1. The steric effect of the methyl group in the six-position of the N-oxide ring is considered in comparing these structures to complexes of 2-thiopyridine N-oxide.     

ZnS晶体的化学气相沉积生长

本文报道了用化学气相沉积(CVD)法生长ZnS透明多晶体的实验结果,对生长的晶体的物理化学性能进行了测试,讨论了化学气相沉积工艺中影响ZnS晶体质量的因素.结果表明:选用固体硫作原料,用化学气相沉积方法,可以沉积出透明ZnS多晶体;它的透过性能极其优异,在6.2μm处无吸收峰,在中、长波红外透过率可达70;以上.     

Thermally activated delayed fluorescence host materials based on triphenylphosphine oxide derivatives

Abstract

Novel thermally activated delayed fluorescence (TADF) host molecules for blue electrophosphorescence were developed by combining the electron donor acridine derivatives with the electron acceptor triphenylphosphine oxide unit in a single molecule based on density functional theory. We obtained the energies of the first excited singlet (S₁) and triplet (T₁) states of the TADF materials by performing procedures in accordance with density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations to the ground state using dependence on the charge transfer amounts for the optimal Hartree-Fock percentage in the exchange-correlation of TD-DFT. Using DFT and TD-DFT calculations, the significant separation between the HOMO and LUMO caused a small difference in energy (ΔE_ST) between the S₁ and T₁ states. The host molecules retained high triplet energy and showed great potential for use in blue phosphorescent organic light-emitting diodes. The results also showed that these molecules are promising TADF host materials because they demonstrate a low barrier to hole and electron injection, balanced charge transport for both holes and electrons, and small ΔE_ST.     

碲锌镉单晶体的正电子寿命研究

用正电子湮没技术(PAT)研究了原料富Cd改进布里奇曼法生长的碲锌镉单晶样品退火前后的缺陷.刚生长的样品缺陷寿命值较高,其内部存在的点缺陷主要是占优势的Cd空位,用富Cd同成份源Cd1-xZnxTe气氛对样品在不同温度下等时退火后,发现样品的正电子寿命参数对退火温度表现出很强的依赖关系,通过对样品退火过程中空位的迁移、聚集及消失情况分析,得出较适宜的退火温度约为700℃.