A novel micro accelerometer with adjustable sensitivity based on resonant tunneling diodes

Resonant tunnelling diodes (RTDs) have negative differential resistance effect, and the current--voltage characteristics change as a function of external stress, which is regarded as meso-piezoresistance effect of RTDs. In this paper, a novel micro-accelerometer based on AlAs/GaAs/In_0.1Ga_0.9As/GaAs/AlAs RTDs is designed and fabricated to be a four-beam-mass structure, and an RTD-Wheatstone bridge measurement system is established to test the basic properties of this novel accelerometer. According to the experimental results, the sensitivity of the RTD based micro-accelerometer is adjustable within a range of 3 orders when the bias voltage of the sensor changes. The largest sensitivity of this RTD based micro-accelerometer is 560.2025 mV/g which is about 10 times larger than that of silicon based micro piezoresistive accelerometer, while the smallest one is 1.49135 mV/g.     

基于纳米锥森林结构的表面增强拉曼散射透明器件研究

具有无损、超灵敏和实时检测优点的表面增强拉曼散射(SERS)器件具有重要研究意义。目前,针对SERS器件的大部分研究都围绕着非透明的器件展开。使用此类器件检测高浓度试剂时,激光只能从正面入射。这意味着入射激光需要穿透被测试剂分子层才能到达位于其下方的金属纳米结构表面,因此用于激发金属纳米结构表面等离子体共振(SPR)的激光能量被减弱,相应地,SERS光谱信号也被减弱;此外,SERS光谱信号因被测试剂分子层的遮挡,无法高效返回到电荷耦合元件(CCD)中,再次被大幅度减弱,甚至有可能完全无法被检测到。相比之下,如果使用透明SERS器件,检测过程中将被测试剂分子置于器件正面,激光从器件背面入射,此时高浓度被测试剂分子层对入射激光和SERS光谱信号的干扰最小。这种情况下,可以得到较好的光谱信号。通过在石英基底上旋涂聚酰亚胺(PI)层,然后通过氧等离子体对PI层进行无掩模轰击,在石英基底上自行生成纳米纤维掩模,配合反应离子刻蚀工艺(RIE)制备了石英纳米锥森林结构。之后,通过金属纳米颗粒溅射工艺,得到SERS透明器件。对于该SERS透明器件,在测试过程中,拉曼激光可从器件的正面以及背面分别入射。初步的测试结果表明,对于罗丹明6G(R6G)在10^-3~10^-6 mol·L^-1这一浓度范围内,背面入射方式收集的SERS光谱信号强度高于正面入射方式。另外,进一步研究了该SERS透明器件背面检测的一致性,得到了良好的结果,证明了其在实际生化检测中的可行性。这一工作有望扩展SERS在分析物检测领域中的应用。     

基于等离激元多重杂化效应的光吸收结构

近年来,以聚合物为代表的高分子材料由于具有比其他光吸收材料(如半导体材料、碳基材料以及贵金属纳米材料)更好的柔性和粘弹性而受到广泛关注.本文基于等离子体再聚合技术和磁控溅射工艺在聚合物材料层上制备了具有等离激元多重杂化效应的光吸收结构,该结构具有宽谱高吸收特性.该结构的制备工艺简单易行,对不同聚合物材料具有通用性,在光学器件领域具有广泛的应用前景.     

Graphene-based heterojunction for enhanced photodetectors

Graphene has high light transmittance of 97.7% and ultrafast carrier mobility, which means it has attracted widespread attention in two-dimensional materials. However, the optical absorptivity of single-layer graphene is only 2.3%, and the corresponding photoresponsivity is difficult to produce at normal light irradiation. And the low on—off ratio resulting from the zero bandgap makes it unsuitable for many electronic devices, hindering potential development. The graphene-based heterojunction composed of graphene and other materials has outstanding optical and electrical properties, which can mutually modify the defects of both the graphene and material making it then suitable for optoelectronic devices. In this review, the advantages of graphene-based heterojunctions in the enhancement of the performance of photodetectors are reviewed. Firstly, we focus on the photocurrent generation mechanism of a graphene-based heterojunction photodetector, especially photovoltaic, photoconduction and photogating effects. Secondly, the classification of graphene-based heterojunctions in different directions is summarized. Meanwhile, the latest research progress of graphene-transition metal dichalcogenide (TMD) heterojunction photodetectors with excellent performance in graphene-based heterostructures is introduced. Finally, the difficulties faced by the existing technologies of graphene-based photodetectors are discussed, and further prospects are proposed.