Study of Ge2Sb2Te5 Film for Nonvolatile Memory Medium

The amorphous Ge2Sb2Te5 film with stoichiometric compositions was deposited by co-sputtering of separate Ge, Sb, and Te targets on SiO2/Si (100) wafer in ultrahigh vacuum magnetron sputtering apparatus. The crystallization behavior of amorphous Ge2Sb2Te5 film was investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and differential scanning calorimetry (DSC). With an increase of annealing temperature, the amorphous Ge2Sb2Te5 film undergoes a two-step crystallization process that it first crystallizes in face-centered-cubic (fcc) crystal structure and finally fcc structure changes to hexagonal (hex) structure. Activation energy values of 3.636±0.137 and 1.579±0.005 eV correspond to the crystallization and structural transformation processes, respectively. From annealing temperature dependence of the film resistivity, it is determined that the first steep decrease of the resistivity corresponds to crystallization while the second one is primarily caused by structural transformation from     

Structural and electrical measurements of CdZnSe composite

TheI—Vcharacterization and the electrical resistivity of selenium rich Se₈₅Cd_15-xZn_x (x = 0, 3, 7, 11 and 15) system at room temperature have been studied. Samples were obtained using melt cooling technique. So prepared samples were then characterized in terms of their crystal structure and lattice parameter using X-ray diffraction method. The materials were found to be poly crystalline in nature, having zinc blend structure over the whole range of zinc concentration. The measurements ofI—V bdcharacteristics have been carried out at different temperatures from room to 140°C. The electrical resistivity of the samples with composition at room temperature has been found to vary between maximum 2.7 x 10⁸ Ωm and minimum 7.3 x 10⁵ Ωm and shows a maximum at 3 at. wt.% of Zn. The carrier activation energy of the samples with composition has also been determined and found to vary from 0.026 eV to 0.111 eV.     

透明导电ZnO∶Al(ZAO)纳米薄膜的性能分析

用直流反应磁控溅射法制备ZAO纳米薄膜 ,对这种薄膜进行了XRD分析 ,并对其光、电性能作了详细的研究。结果表明 :ZAO薄膜的结构为标准的ZnO纤锌矿相 ,没有Al2 O3 相出现 ;其最低电阻率为 4 5× 10 -4Ω·cm、可见光透射率在 80 %以上 ,红外波段的反射率达 70 %以上 ,是优质的透明导电膜     

基体温度对磁控溅射沉积ZAO薄膜性能的影响

利用中频交流磁控溅射方法 ,采用氧化锌铝陶瓷靶材 [w(ZnO) =98%、w(Al2 O3 ) =2 % ]制备了ZAO(ZnO∶Al)薄膜 ,观察了基体温度对ZAO薄膜的晶体结构、电学和光学性能的影响 ,采用X射线衍射仪对薄膜的结构进行了分析 ,采用光学分度计和电阻测试仪测量了薄膜的光学、电学特性 ,采用霍尔测试仪测量了薄膜的载流子浓度和霍尔迁移率。结果表明 :沉积薄膜时的基体温度对薄膜的结构、结晶状况、可见光透射率以及导电性有较大的影响。当基体温度为 2 5 0℃ ,Ar分压为 0 8Pa时 ,薄膜的最低电阻率为 4 6× 10 -4Ω·cm ,方块电阻为 35Ω时 ,可见光 (λ =5 5 0nm)透射率高达 92 0 %。     

功率密度对中频磁控溅射制备的氧化锌镓薄膜性能的影响

利用中频磁控溅射方法,溅射Ga2O3含量为6.7wt%的氧化锌镓陶瓷靶材,在低温下(约40℃)制备了ZGO薄膜.考察了溅射功率密度对ZGO薄膜的晶体结构、电学和光学性能的影响.结果表明:溅射功率密度对薄膜的结构、红外反射以及导电性能有较大影响.当溅射功率密度为3.58W/cm2,氩气压力为0.8Pa时,薄膜的电阻率低达1.5×10-3Ω·cm,方块电阻为23Ω时,可见光(λ＝400nm～800nm)平均透过率高于90%.     

Effect of oxygen partial pressure on the microstructural and physical properties on nanocrystalline tin oxide films grown by plasma oxidation after thermal deposition from pure Sn targets

In this work, microstructural and physical properties were studied in the tin oxide films deposited by thermal evaporation of Sn films on stainless steel substrates followed by in situ D.C. plasma oxidation at 200 °C substrate temperature. The surface properties were studied by scanning electron microscopy, X-ray diffraction, atomic force microscopy and four-point probe electrical resistivity. The typical calculated grain size of the films deposited by thermal evaporation was between 28 nm and 66 nm and the texture structure was found to be dependent on the thermal deposition pressure. A cassiterite structure of SnO₂ was produced by D.C. plasma oxidation with the main diffraction peaks of the (101), (200), (211), (310) and (221) planes at the 25% and 50% O₂ partial pressure conditions. However, at 12.5% O₂ partial pressure oxidation conditions, amorphous tin oxide structure and crystalline SnO phases were detected. Increasing thermal deposition pressure resulted in preferential texture formation at (211) and (310) planes. The surface structure investigation of the produced films by SEM and AFM studies showed large SnO₂ islands with approximately 1.0 μm and 1.5 μm sized nodules, and they are called as grape-like structures. The grape-like grains possess nano grains, which are between 20 nm and 30 nm in diameter calculated by Scherer's formula. The grape-like grains were seen to be separated by large cavities and the size of these cavities and nano grains was seen to be larger when the O₂ partial pressure is increased. The four-point probe resistivity of the films, grown at different oxidation temperatures, decreased with the increase in oxygen partial pressure. The values of resistivity for SnO₂ phase were measured as low as 10⁻⁵ Ω-cm and observed to decrease with increasing thermal deposition pressure and oxygen partial pressure.     

Optical and electrical properties of p-type transparent conducting CuAlO2 thin film

P-type transparent conducting CuAlO₂ thin films were prepared by e-beam evaporation and wet-oxidation technique. CuAlO₂ film was preferentially (006) oriented after wet-oxidation. The transmittance varied from 20 to 85% and the resistivity varied from 5 × 10^− 3 to 4 Ω cm with wet-oxidation conditions. The nature of p-type films was confirmed by the positive hall coefficient. Optical band gap was estimated to be in the range of 3.96-4.20 eV. These behaviors were due to the decrease of oxygen deficient state in the film as oxidation progresses. Microstructural observations of films showed smooth morphology with 23.2-29.7 Å rms roughness.     

双位组合四探针法测量硅片电阻率

本文研究用双位组合四探针测量硅材料薄片电阻率的新技术，提出新的计算公式和厚度修正原理。用双位组合法测量不同厚度硅样品所得结果与常规四探针法测得的结果相比较表明，用双位组合法测量较厚（Ｗ／Ｓ＞０．６）样品时，非但不能直接套用常规的厚度计算方法，而且还必须采取新的厚度修正。本文给出两种双位组合法的计算公式，分析新的厚度修正原理，给出测试结果，得出相应结论。