Research On Hot Electron Emmission At Solid-state Interfaces Based On Schottky Nano-heterojunctions

In the hot electron device at solid state interface made of Schottky nano-heterostructure,the electrons cross the Schottky barrier in ballistic transport mode,and the transport process occurs within the average free path range of electrons.In turn,a hot electron current is formed by the closed external circuit.Because the Schottky nano-heterojunction can be prepared on a silicon substrate and the thickness is about 20 nm,and it is suitable for integration applications.However,traditional studies of hot electron usually use CO,H₂ and other gases that are difficult to store and transport as raw materials.At the same time,as a common industrial raw material,methanol has a wide range of sources and low cost,and its liquid state at normal temperature and pressure makes it easy to popularize.In order to apply methanol as a raw material to the research system of hot electron at solid interfaces,the following works are studied in this paper:(1)Design and build a system for the characterization of the hot electron device and the test of the hot electron current.Based on the special design for low current test environment,the problem of excessive error of current test in methanol atmosphere is overcome,and the variable temperature test of room temperature-600? can be realized.Systematic auxiliary characterization includes XRD,SEM,TEM,AFM,XPS,and a catalyst evaluation system based on chromatograph is built.Combining the adsorption and chemical reaction process,a systematic analysis of the hot electron emission process at solid-state interface is carried out by the test system.(2)Pt/Si Schottky nano-heterojunction are designed and manufactured by means of magnetron sputtering from hard mask experient.The thickness of the Pt layer is 20 nm,and methanol/air mixed gas flux is used as the raw material.The hot electron current is instable and has no temperature dependence.Further analysis shows that the crystallinity of the Pt layer is low(22.63%),the binding energy is high(71.70 e V),and the surface roughness is low(0.243 nm).The experimental and theoretical analysis results show that the hot electron transport phenomenon of Pt/Si Schottky nano-heterojunction is in accordance with the molecular adsorption theory.(3)Pt₃Cu/Si Schottky nano-heterojunctions are designed and manufactured by means of magnetron sputtering from hard mask experient.The thickness of the Pt₃Cu layer is 20 nm.The methanol/air mixed gas flux is used as the raw material.The hot electron current has a certain degree of stability and temperature dependence.As the heating temperature increases,the current value increases rapidly and has more time stability.Further analysis shows that the crystallinity of the Pt₃Cu layer is high(64.70%),and has low binding energy(71.38 e V)and high surface roughness(0.402 nm).The experimentally tested Pt₃Cu/Si Schottky barrier height is also low,which is conducive to the formation of a stable current by hot electrons crossing the barrier.The experimental and theoretical analysis results show that the hot electron emission phenomenon of Pt₃Cu/Si Schottky nano-heterojunctions conform to the theory of hot electron transport in non-adiabatic system at a specific temperature range.(4)Further research on the hot electron current using Pt₃Cu/Si Schottky nano-heterojunction is investigated at different temperatures,and mechanism that affects its current change is explored at various temperature sections.The results show that the current change in the low temperature section is in accordance with the trend of Arrhenius formula,and it is also affected by molecular adsorption.In the high temperature section,the current change is mainly affected by changes in the morphological characteristics of the heterojunctions.Compared with the Pt/Si Schottky nano-heterojunction,the introduction of Pt3Cu is more conducive to the methanol oxidation reaction.The methanol hot electron emission based on the Pt₃Cu/Si Schottky nano-heterojunction is more likely to form a stable current.For the future,it provides a low-cost,high-security option for the research and application of hot electron emission at solid-state interface.