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(융대원 세미나 공고)Epitaxial graphene on SiC for quantum metrology
작성자 : 관리자작성일 :2012-05-18 12:51:13조회수 : 3525 : 전체

Title : Epitaxial graphene on SiC for quantum metrology

 

Speaker : Karin Cedergren (Post Doc. at Chalmers University of 

                                   Technology, Sweden)

Date & Time : 2012.  5.  21.  월요일  15:30

Where : 융대원 D-111

                     

Abstract

Graphene, in the role of a 2D electron system, has shown to have interesting properties for quantum metrology as a new material for quantum resistance standards. In this talk I will give an overview of how the quantum Hall effect is used for resistance standard and focus on Hall bar devices fabricated using epitaxial graphene on SiC. In these devices we have measureda quantum Hall resistance quantization accuracy of three parts per billion at 300mK.Furthermore, by controllingthe carrier concentration by a novel photosensitiveheterostructure of epitaxial graphene grown on silicon carbide combined with two polymers, we have changed the carrier concentration in graphene by a factor of 50 in a non-invasive, non-volatile, and reversible way. The newly developedphotochemical gating has already helped to improve the robustness of a graphene resistance standard, further improving the quantization accuracy by a factor of 30. By the implementation of these refinements it was possible to perform the first direct comparison of the integer quantum Hall effect (QHE) in epitaxial graphene with that in GaAs/AlGaAsheterostructures. No difference was found in the quantized resistance value within the relative standard uncertainty of the measurement of 8.6×10−11, this being the most stringent test of the universality of the Quantum Hall Effect in terms of material independence.

 

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