Study Of Quantal Transport Properties Of Ge/Si Core/Shell Structure Modified By Amino Acid

The properties of quasi-one dimensional(1D)semiconductor nanowire is different from bulk materials,and more and more people pay close attention to them in nanoelectronics,optoelectronics and other fields due to their structure,electronic,transport and large surface-to-volume ratio properties.In one-dimensional nanomaterials,the core/shell nanowires(CSNWS)play an important role.So far,among lots of having been fabricated CSNWs,Ge/Si CSNWs arouse people's interest and has been used in many fields since they are easy to integrate into Si technology.Multitudinous research results show that the nanowires are good sensor materials,but the sensing characteristics of Ge/Si core/shell structure is researched so poor.For these reasons,in this thesis,based on density functional theory and non-equilibrium Green's function,we investigate the transport properties of amino acid modified or not modified Ge/Si core/shell structure and discuss their possibility as a sensor or a molecular switch.The main outline and results of our reaserches are listed blow.Firstly,we study the transport properties of amino acid not modified Ge/Si core/shell structure.After calculated and analyzed the I-V curve,transmission and DOS of four kinds of length models,we find that the length of M=1 and 2 of the Ge/Si core/shell structure are metal,but the length of M=3 and 4 of this structure are semiconductor.In addition,all these four models can form electronic quantum wells in core region,so the electron only transfer in Ge material.These are very beneficial for future high speed devices,owing to the mobility of carriers in Ge higher than it in Si.Afterwards,we calculate and study the transport properties of 20 types of amino acid modified Ge/Si core/shell structure under low biases voltage(0.1V).The results of different models show that the I-V curves of all the models are linear under this biases,but the conductance is different,which suggests that amino acids can regulate the Ge/Si core/shell structure conductance.This means that Ge/Si core/shell structure is sensitive to amino acids under low biases.In other words this structure can be used for the study of high sensitivity amino acid sensor.Then,on the basis of amino acid modified Ge/Si core/shell structure,we further investigate transport properties of some new models which is the-NH2 of amino acids adsorbed an H ion.Using Glycine and Serine as examples,from the research results we can find that there is a significant change in transport properties of these system and all the structures exhibit characteristics of a molecular switch.These devices appear the ?on? or ?off? states with the redox reaction,which can be used for molecular logic circuit.In addition,the structure of the device is sensitive to the PH value of the environment,indicating that it can be used as a H ion sensor.