Direct growth of GaN films on Si(001) substrate at low temperatures (620～720℃) by electron cyclotron resonance (ECR) microwave plasma enhanced metalorganic chemical vapor deposition (PEMOCVD).The crystalline phase s...Direct growth of GaN films on Si(001) substrate at low temperatures (620～720℃) by electron cyclotron resonance (ECR) microwave plasma enhanced metalorganic chemical vapor deposition (PEMOCVD).The crystalline phase structures of the films are investigated.The results of high resolution transmission electron microscopy (HRTEM) and X ray diffraction (XRD) indicate that high c axis oriented crystalline wurtzite GaN is grown on Si(001) but there is an amorphous layer formed naturally at GaN/Si interface.Both faces of the amorphous layer are flat and sharp,and the thickness of the layer is 2nm approximately cross the interface.The analysis supports that β GaN phase is not formed owing to the N x Si y amorphous layer induced by the reaction between N and Si during the initial nucleation stage.The results of XRD and atomic force microscopy (AFM) indicate that the conditions of substrate surface cleaned in situ by hydrogen plasma,GaN initial nucleation and subsequent growth are very important for the crystalline quality of GaN films.展开更多
As a novel technique in engineering,Virtual Prototyping(VP)was applied to the design of cyclotrons with the purpose of shortening the development period and reducing the costs for physical prototypes.The advances in V...As a novel technique in engineering,Virtual Prototyping(VP)was applied to the design of cyclotrons with the purpose of shortening the development period and reducing the costs for physical prototypes.The advances in VP techniques for compact cyclotron design in HUST are introduced.The idea of multi-domain collaborative design was proposed.This paper describes the pythonic mixed language programming approach to develop the VP integrate platform.Under this platform,the optimization design of main magnet,RF cavity and central region of cyclotrons is to be achieved.展开更多
文摘Direct growth of GaN films on Si(001) substrate at low temperatures (620～720℃) by electron cyclotron resonance (ECR) microwave plasma enhanced metalorganic chemical vapor deposition (PEMOCVD).The crystalline phase structures of the films are investigated.The results of high resolution transmission electron microscopy (HRTEM) and X ray diffraction (XRD) indicate that high c axis oriented crystalline wurtzite GaN is grown on Si(001) but there is an amorphous layer formed naturally at GaN/Si interface.Both faces of the amorphous layer are flat and sharp,and the thickness of the layer is 2nm approximately cross the interface.The analysis supports that β GaN phase is not formed owing to the N x Si y amorphous layer induced by the reaction between N and Si during the initial nucleation stage.The results of XRD and atomic force microscopy (AFM) indicate that the conditions of substrate surface cleaned in situ by hydrogen plasma,GaN initial nucleation and subsequent growth are very important for the crystalline quality of GaN films.
文摘As a novel technique in engineering,Virtual Prototyping(VP)was applied to the design of cyclotrons with the purpose of shortening the development period and reducing the costs for physical prototypes.The advances in VP techniques for compact cyclotron design in HUST are introduced.The idea of multi-domain collaborative design was proposed.This paper describes the pythonic mixed language programming approach to develop the VP integrate platform.Under this platform,the optimization design of main magnet,RF cavity and central region of cyclotrons is to be achieved.
