Characterization of CuGaSe2 thin films grown by MOCVD

CuGaSe₂ thin films have been grown by metalorganic chemical vapor deposition (MOCVD), from three organometallic precursors. Samples of about 1-2 μm thick are codeposited onto Pyrex and Mo-coated soda lime glass. A large range of compositions was investigated and characterized. Stoichiometric CuGaSe₂ thin films are single-phased and their optical bandgap is about 1.68 eV. The features of the films are presented in relation with their composition. XRD spectra always exhibit a preferential orientation along the (112) plane. Secondary phases have been observed: Cu₂Se for Cu-rich films, CuGa₃Se₅ for Ca-rich films. Observation of the morphology reveals larger polyhedral grains for Cu-rich films becoming platelet-shaped and tilted for Ga-rich compounds. The optical properties are also sensitive to the compositional changes and related to the eventual presence of binary phases. The gap increases with the Ga-content. The CuGa₃Se₅, phase exhibit a gap of about 1.85 eV. All the samples have a p-type conductivity     

黄色荧光粉CaBi_2Ta_2O_9:Dy~(3+)的制备及发光性能

采用高温固相反应法制备了Dy3+掺杂铋层结构铁电氧化物CaBi2Ta2O9(CBTO)荧光粉。分别对样品进行了X射线衍射(XRD)分析、扫描电镜(SEM)测试和荧光光谱(PL)的测定。研究表明:荧光粉CBTO:Dy3+的最强激发峰为450 nm,与商用蓝光LED的发射光波长相匹配,发射带峰值位于574 nm,对应于Dy3+的电偶极跃迁4F9/2→6H13/2。分析了Dy3+摩尔分数对样品发光强度的影响,其最佳摩尔分数为7%,根据Dexter理论分析其浓度猝灭机理为电偶极-电偶极相互作用。分别研究了电荷补偿剂Li+、Na+和K+对CBTO:Dy3+发射光谱的影响,结果显示不同的电荷补偿剂均能不同程度地提高样品的发光强度。     

Sensor effect in YBa2 Cu3 Oy

The high-T_c superconducting material YBa₂ Cu₃ O_y, well known as a 1–2–3 compound, shows other very interesting properties. One of them is very strong conductivity-oxygen content dependence. On the basis of our previous measurements, an investigation of dilatation synthesis, X-ray diffraction (XRD) analysis and conductivity measurements were performed. The results on quenched and slowly cooled samples show a phase transition region and an obvious interdependence between conductivity, unit cell volume and oxygen content.     

Characterization of the annealing impact on La2O3/HfO2 and HfO2/La2O3 stacks for MOS applications

The impact of various rapid thermal annealing used during the integration on the La₂O₃/HfO₂ and HfO₂/La₂O₃ stacks deposited by Atomic Layer deposition was analyzed. The consequences of lanthanum localization in such stacks on the evolution of the films during the rapid thermal annealing are investigated in term of morphology, crystalline structure, silicate formation and film homogeneity as a function of the depth. It appeared that the La₂O₃ location has an impact on the temperature of the quadratic phase formation which could be linked to the formation of SiOHfLa silicate and the resistance of the films to dissolution in HF 0.05 wt%.     

H2/O2 plasma on polysilicon thin-filmtransistor

It is reported for that H₂ plasma followed by O₂ plasma is more effective for passivating grain boundary states in polysilicon thin film. Polysilicon thin-film transistors (TFTs) made after H₂/O₂ plasma treatment can exhibit a turn-on threshold voltage of -0.1 V, a subthreshold swing of 0.154 V/decade, an ON/OFF current ratio I_on/I_off over 1×10⁸, and an electron mobility of 40.2 cm² /V-s     

混响室中混响时间测量测点位置的探讨

在分析了混响室中引起混响时间测量随机误差之后,提出将测点置于混响室角点上,这是更为合理的测量方法。     

TiO_2/SiO_2、ZrO_2/SiO_2多层介质膜光学损耗及激光损伤研究

以TiO_2/SiO_2及ZrO_2/SiO_2多层介质膜为例,测试了不同工艺条件及不同膜系结构下薄膜样品的光学损耗及激光损伤阈值,同时对实验结果作了初步的分析讨论.     

氮气或氧气气氛退火的氧化铪材料电荷泄漏情况研究

本文中, 使用开尔文探针显微镜,研究了不同退火气氛(氧气或氮气)情况下氧化铪材料的电子和空穴的电荷保持特性。与氮气退火器件相比,氧气退火可以使保持性能变好。横向扩散和纵向泄露在电荷泄露机制中都起了重要的作用。 并且,保持性能的改善与陷阱能级深度有关。氮气和氧气退火情况下,氧化铪存储结构的的电子分别为0.44 eV, 0.49 eV,空穴能级分别为0.34 eV, 0.36 eV。 最后得到,不同退火气氛存储器件的电学性能也与KFM结果一致。对于氧化铪作为存储层的存储器件而言,对存储特性的定性和定量分析,陷阱能级,还有泄漏机制研究是十分有意义的。     

Kinetics of chemical vapor deposition of WSix films from WF6 and SiH2Cl2: Effect of added H2, SiH4, and Si2H6

This paper describes reaction kinetics of chemical vapor deposition of WSi_x films from WF₆ and SiH₂Cl₂, focusing on the effect of added H₂, SiH₄, and Si₂H₆ as an active reaction initiator. Our studies indicate that the temperature at which film formation is extinguished, T_ex, can be lowered by introducing H₂ instead of the standard Ar carrier gas. For a SiH₂Cl₂/WF₆ pressure ratio of 20, H₂ addition changed the deposition mode from selective W deposition to blanket WSi_x deposition. The added H₂ also improved the step-coverage profile for substrate temperatures below 600 °C. Measured step coverage profiles indicate that the activation energy of deposition species was 147 kJ/mol. Adding either SiH₄ or Si₂H₆ can assist the film-forming reactions to achieve acceptable Si/W atomic composition ratios. Under these conditions, the residual fluorine concentration remained at acceptably low levels that are typical of conventional WF₆/SiH₂Cl₂ CVD processes.     

脉冲CO_2激光作用下光气在BCl_3中的分解与生成

研究了在脉冲能量为0.8焦耳的TEA CO_2激光作用下BCl_3中光气的分解与生成。峰值功率密度约10~6瓦/厘米~2的脉冲CO_2激光,既不引起BCl_3中COCl_2的分解,也不引起BOl_3中的CO和Cl_2生成COCl_2。在焦点区峰值功率密度约10~8瓦/厘米~2的CO_2激光,则引起BOl_3中光气的分解和生成。     

Nonlinear optical properties ofK2La(NO3)5.2H2O and K2Ce(NO3)5.2H2O

The harmonic generating properties of potassium lanthanum nitrate (KLN) and potassium cerium nitrate (KCN) are described. These crystals have much larger nonlinear coefficients than potassium dihydrogen phosphate (KDP) and are nearly noncritically phase matched at room temperature for Type I frequency doubling of 1.064-μm light, and for Type II doubling of light near 0.95 μm. Thus, these crystals are useful for generating blue-green light by frequency doubling high-power near-infrared lasers. The crystal growth of KLN and KCN are described by the three component phase diagrams. Crystallographic data for KCN that confirms its structural similarity to KLN are presented. The optical absorption spectra of the two materials are discussed, and the linear refractive indexes are given     

Time-dependent-dielectric-breakdown characteristics of Hf-doped Ta2O5/SiO2 stack

The Time-Dependent-Dielectric Breakdown (TDDB) characteristics of MOS capacitors with Hf-doped Ta₂O₅ films (8 nm) have been analyzed. The devices were investigated by applying a constant voltage stress at gate injection, at room and elevated temperatures. Stress voltage and temperature dependences of hard breakdown of undoped and Hf-doped Ta₂O₅ were compared. The doped Ta₂O₅ exhibits improved TDDB characteristics in regard to the pure one. The maximum voltage projected for a 10 years lifetime at room temperature is −2.4 V. The presence of Hf into the matrix of Ta₂O₅ modifies the dielectric breakdown mechanism making it more adequate to the percolation model. The peculiarities of Weibull distribution of dielectric breakdown are discussed in terms of effect of three factors: nature of pre-existing traps and trapping phenomena; stress-induced new traps generation; interface layer degradation.     

Chemical Solution Deposition of Y2 Ti2O7–La 2Zr2 O7 Composite Buffer Layers

Chemical solution deposition, a very useful method for oxide film growth, is used to fabricate Y₂Ti₂O₇ (YTO)-La₂Zr₂O₇ (LZO) composite buffer layers on NiW (200) substrates. It is found that the orientation of the YTO layer is epitaxially related to the orientation of the LZO-NiW template. When YTO is prepared on a 900degC -annealed LZO layer, the orientation of the YTO is (222); however, the (400) oriented YTO layer is obtained when it is deposited on a 1000degC-annealed LZO-NiW template. These results suggest that the YTO orientation can be tuned by the LZO orientation and that YTO can be considered as one of the cap layers for coated conductors.     

C_(60)薄膜荧光非单指数衰减的四能级模型研究

研究了高真空蒸发技术制备的Ｃ６０薄膜在温度自１２７Ｋ至室温范围的时间分辨荧光光谱，在１２７Ｋ时，Ｃ６０薄膜的荧光峰处于７３０ｎｍ且其时间弛豫特性呈单指数衰减行为；当温度上升时，荧光峰红移，其弛豫特性明显偏离单指数行为。采用四能级模型处理Ｃ６０激发态的弛豫行为，得到双指数衰减规律，并用双指数函数对实验结果进行了拟合，结果表明，当温度上升时，单重态至三重态Ｔ１的系间交叉速率明显增大     

Photoluminescence of AlGaAs alloy grown by LP-MOVPE at different temperatures using TBA in N2 ambient

High quality of Al_xGa_1−xAs alloys have been grown by the LP-MOVPE using tertiary-butyl arsine as group V precursor in 100% nitrogen ambient. The photoluminescence (PL) properties of Al_0.25Ga_0.75As alloy grown at different temperature have been studied. The PL peak emission intensity of the samples increases with the substrate growth temperature initially and saturated at the growth temperature 760°C. The emission intensity decreases when further increase the temperature. This is attributed to the oxygen content in the samples.     

环F2+uF2+…+uk-1F2上常循环自对偶码

最近,剩余类环上的常循环码及常循环自对偶码引起了编码学者的极大关注.本文首先利用一些相关的线性码,建立了一类特殊有限链环上长为N的常循环自对偶码的一般理论,利用其结果给出了该环上长为N的(1+uλ)-常循环自对偶码存在的充分条件,得到了该环上长为N的一些常循环自对偶码,并给出了其生成多项式.     

Low-frequency noise in Si0.7Ge0.3 surface channel pMOSFETs with ALD HfO2/Al2O3 gate dielectrics

Low-frequency noise was characterized in Si_0.7Ge_0.3 surface channel pMOSFETs with ALD Al₂O₃/HfO₂/Al₂O₃ stacks as gate dielectrics. The influences of surface treatment prior to ALD processing and thickness of the Al₂O₃ layer at the channel interface were investigated. The noise was of the 1/f type and could be modeled as a sum of a Hooge mobility fluctuation noise component and a number fluctuation noise component. Mobility fluctuation noise dominated the 1/f noise in strong inversion, but the number fluctuation noise component, mainly originating from traps in HfO₂, also contributed closer to threshold and in weak inversion. The number fluctuation noise component was negligibly small in a device with a 2 nm thick Al₂O₃ layer at the SiGe channel interface, which reduced the average 1/f noise by a factor of two and decreased the device-to-device variations.     

氧化钌/氧化锰复合电极材料的性能研究

采用溶胶-凝胶法和水热合成反应法分别制备了氧化钌和氧化锰电极材料。进而采用胶体法制备了不同配比的氧化钌/氧化锰复合电极材料。利用扫描电镜和X射线衍射仪分别对电极材料的形貌及其结构进行表征。通过循环伏安法、恒流充放电、交流阻抗谱对复合电极进行电化学性能测试。结果表明：在氧化钌中加入适量的氧化锰的有助于降低氧化钌的成本和提高氧化钌的阻抗特性,当氧化锰的含量为60wt%时,在38%的H2SO4溶液中,扫描速度为20mV/s时,复合电极的比电容为438F/g,内阻为0.304Ω,且在经过300次循环充放电后,比容量仍保持92.5%,可作为较理想的超级电容器电极材料。     

Pseudopotential study of PrO2 and HfO2 in fluorite phase

Praseodymium and hafnium oxides are prospective candidates to subsitute SiO₂ in decanano MOSFET transistors. We report first ab initio pseudopotential band structure calculations for these materials. We find that fluorite phases of PrO₂ and HfO₂ have similar electronic structures. The important difference is a narrow sub-band forming the conduction band bottom in PrO₂ but absent in HfO₂. Electrons in this f-type sub-band have large masses. This explains why ultrathin epitaxial Pr oxide films have low leakage in spite of a relatively small conduction band offset (1 eV) between the oxide and the Si substrate.     

Ga2O3(Gd2O3)/InGaAsenhancement-mode n-channel MOSFETs

We have demonstrated the first Ga₂O₃(Gd₂O₃) insulated gate n-channel enhancement-mode In_0.53Ga_0.47As MOSFET's on InP semi-insulating substrate. Ga₂O₃(Gd₂ O₃) was electron beam deposited from a high purity single crystal Ga₅Gd₃O₁₂ source. The source and drain regions of the device were selectively implanted with Si to produce low resistance ohmic contacts. A 0.75-μm gate length device exhibits an extrinsic transconductance of 190 mS/mm, which is an order of magnitude improvement over previously reported enhancement-mode InGaAs MISFETs. The current gain cutoff frequency, f_t, and the maximum frequency of oscillation, f_max, of 7 and 10 GHz were obtained, respectively, for a 0.75×100 μm² gate dimension device at a gate voltage of 3 V and drain voltage of 2 V