InAs/GaAs (1 1 1)A heteroepitaxial systems

We studied the structural, electrical, and mechanical properties of an InAs thin film grown on GaAs (1 1 1)A substrates by molecular beam epitaxy. In contrast to conventionally used (0 0 1) surfaces, where Stranski–Krastanov growth dominates the highly mismatched heteroepitaxy, layer-by-layer growth of InAs can be established. One of the largest advantages of this unique heteroepitaxial system is that it provides a two-dimensional electron gas system in the near-surface region without the problem of electron depletion. We review the fundamental properties and applications of this unique heteroepitaxial system.     

聚氯乙烯/炭黑导电复合体系的压阻行为

研究了聚氯乙烯/炭黑(PVC/CB)导电复合体系在单轴压力作用下的压阻行为,发现CB含量对电阻-机械响应具有显著的影响.当CB含量低于渗流阈值时,PVC/CB复合材料呈现PPC效应;而高于渗流阈值时,呈现NPC效应.在渗流阈值附近,单轴压缩可诱导NPC效应的出现,或者抑制PPC效应.     

Anisotropy of Long-term Resistivity Relaxations Induced in p -(0 0 1)GaAs/Al 0.5 Ga 0.5 As by Uniaxial Stress

Anisotropy of the piezoresistance relaxations has been observed in p -(0 0 1)GaAs/Al 0.5 Ga 0.5 As heterostructures. The character of relaxation process depends on the direction of the applied uniaxial compression: after loading along [1 m 1 0] direction the specimen resistance relaxes down to the lower magnitude while after loading along [1 1 0] direction it relaxes up to the higher magnitude. Shubnikov-de Haas oscillations and Hall effect measurements indicate that variation of the carrier concentration j N in the quantum well during relaxation processes has different signs for uniaxial compression along [1 m 1 0] and [1 1 0] directions and correlates with the corresponding change of the resistance. The piezoelectric field that in GaAs can reach the magnitude E =1.152 2 10 6 V/m at uniaxial stress P =1 kbar along d 1 1 0 ¢ directions is supposed to be responsible for the metastable state after loading (unloading) and redistribution of carriers during the relaxation process.     

铝诱导层交换超薄多晶硅薄膜制备及压阻特性

超薄多晶硅薄膜具有优异的压敏特性。铝诱导层交换(ALILE)制备多晶硅薄膜具有成膜温度低薄膜性能优良等特点。利用ALILE方法在玻璃基底上低温条件下制备了50 nm超薄多晶硅(poly-Si)薄膜,并对薄膜微观结构及压阻特性进行了研究。Raman光谱在521 cm-1出现尖锐、对称的特征峰,表明超薄多晶硅薄膜晶化状态良好。此外,在拉曼光谱480 cm-1处没有明显出现a-Si的Raman特征峰也说明制备的poly-Si薄膜样品完全结晶;XRD光谱表明ALILE制备薄膜在(111)和(220)晶向择优生长,晶粒尺寸约5 μm;霍尔效应测试结果表明：ALILE制备薄膜为p型掺杂,空穴浓度为9×1018～6×1019 cm-3;压阻特性研究表明：ALILE超薄多晶硅薄膜应变系数(GF)达到了60以上,且与薄膜厚度相关;应变温度相关系数(TCGF)在-0.17～0%℃范围内;电阻温度相关系数(TCR)在-0.2～-0.1%℃范围内。ALILE超薄多晶硅薄膜具有GF大、TCGF小和TCR小等特点。因此,有望在压力传感器领域得到应用。