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131.
Two-dimensional transition metal disulfides (TMDs) have recently attracted significant research attention due to their rich physical and chemical properties. Graphene has also been studied intensively due to its high electron mobility of ~200000 cm2·V−1·s−1. Since there is no band gap, it is difficult for a graphene-based device to achieve high current on/off ratio. For TMDs, such as MoS2, MoSe2, WSe2, and WS2, the band gaps of these materials can be adjusted according to the number of layers. Since TMD has the advantage of suppressing source-drain tunneling current in an ultra-short transistor and offering superior immunity to short-channel effects, it is also attractive for use as a channel material in Si complementary metal oxide semiconductor (CMOS) devices larger than 22 nm. Among them, MoS2 in single-layer and multi-layer films have been intensively researched for many years. MoS2-based field effect transistors (FETs) with excellent electrical properties have been reported. WS2 has lower in-plane electronic mass than MoS2, MoSe2, and MoTe2, and therefore has potential for higher carrier mobility or higher output current for WS2-based FETs. Experimental research on WS2 is limited compared to MoS2, and more work is needed to further exploit the full potential of WS2-based FETs. Therefore, the electron-phonon interaction and vibration properties of WS2 used in nano-electronic applications and FETs must be investigated. To this end, mono-layer (1L), few-layer (FL), and bulk WS2 films were prepared using mechanical exfoliation from a WS2 crystal. 3M scotch-tape was used for transferring the WS2 films. Detailed temperature-dependent Raman study on 1L, FL, and bulk WS2 films has been conducted using a 514-nm excitation laser. Raman spectroscopy, as an effective and non-destructive approach for phonon vibration study, has been used to evaluate TMDs. The Raman spectra reveal much useful information on the test sample in terms of peak position and spectral shape change. With the film thickness increasing to bulk, the A1g(Γ) and E2g1(Γ) modes show blue-shift and red-shift, respectively, with respect to 1L WS2. Moreover, when the dominant Raman vibration modes swaps between E2g1(Γ) and A1g(Γ), the "cross-over" temperature was identified for 1L, FL, and bulk WS2 films. WS2 shows smaller frequency change Δ between the E2g1(Γ) and A1g(Γ) modes than MoS2, with varying film thickness. The temperature coefficient of the Raman peak position was one magnitude lower for WS2 than MoS2, implying that WS2 has better thermal stability than MoS2. The results of this systematic study provide a physical guidance for WS2-based device design.  相似文献   
132.
For the first time, we introduce a fully quantum mechanical Hamiltonian for a semi-infinite chain model of atoms. We then derive the vibration modes of this model by virtue of the "invariant eigen-operator" method in two different cases, which is concise and revealing.  相似文献   
133.
《物理通报》2007,(9):20-20
触发固体中的相变有各种不同的微妙方法,例如,可用一个光脉冲或电流来注射能够改变一个系统的电子状态的“热”电荷.现在,Rini等人报告了一种很不相同的方法:用太赫兹(THz)辐射来激发一种磁阻性水锰矿中某一振动模式.这一体系具有强关联的电子,在该体系中,即便是晶体结构的微小变化也能对电子性能和磁性能产生深远影响.  相似文献   
134.
使用Gaussian98程序包,在B3LYP/6-311++G**基组水平上对CH3CF2O2+HOO的各反应通道进行了充分研究,过渡态和产物间的联系通过IRC确认.用振动模式分析和电子布居分析对所有反应通道进行了讨论以阐明反应机理.研究结果表明,在能量上CH3CF2CO2+HOO→IM1→TS1→CH3CF2O2H+O2通道最为有利,CH3CF2O2H和O2是主要产物,但CH3OH和CF2O的生成也是可能的.  相似文献   
135.
一种新型Cymbal换能器的研究   总被引:2,自引:0,他引:2  
林书玉  许龙 《声学学报》2011,36(1):27-36
提出并研究了一种新型的Cymbal换能器.与传统的Cymbal换能器相比,该换能器中的压电陶瓷圆盘由一个金属圆环和压电陶瓷圆盘的径向组合体所代替.论文首先探讨了压电陶瓷圆盘和金属圆环组合体的径向振动,用解析方法得出了其径向振动的机电等效电路.在此基础上,得出了新型Cymbal换能器的机电等效电路,并得出了其共振及反共振...  相似文献   
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