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Báo cáo hóa học: " Comparison of nickel silicide and aluminium ohmic contact metallizations for low-temperature quantum transport measurements"

Tuyển tập các báo cáo nghiên cứu về hóa học được đăng trên tạp chí hóa hoc quốc tế đề tài : Comparison of nickel silicide and aluminium ohmic contact metallizations for low-temperature quantum transport measurements | Polley et al. Nanoscale Research Letters 2011 6 538 http www.nanoscalereslett.eom content 6 1 538 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Comparison of nickel silicide and aluminium ohmic contact metallizations for low-temperature quantum transport measurements Craig M Polley Warrick R Clarke and Michelle Y Simmons Abstract We examine nickel silicide as a viable ohmic contact metallization for low-temperature low-magnetic-field transport measurements of atomic-scale devices in silicon. In particular we compare a nickel silicide metallization with aluminium a common ohmic contact for silicon devices. Nickel silicide can be formed at the low temperatures 400 C required for maintaining atomic precision placement in donor-based devices and it avoids the complications found with aluminium contacts which become superconducting at cryogenic measurement temperatures. Importantly we show that the use of nickel silicide as an ohmic contact at low temperatures does not affect the thermal equilibration of carriers nor contribute to hysteresis in a magnetic field. Introduction Aluminium has proven to be a versatile ohmic contact metallization and for a time was the preferred choice for silicon integrated circuits 1 . Aluminium has also been a common contact metallization for a variety of material systems such as gallium nitride 2 silicon carbide 3 and zinc oxide 4 . Owing to this versatility aluminium has seen continued use in silicon-based research including recent quantum dot devices for the study of quantum transport in silicon towards the goal of solid-state quantum computation 5 6 . However the characterization of such devices typically requires millikelvin temperatures well below the normal-superconductor transition temperature of aluminium Tc 1.175 K 7 . Below this temperature the aluminium contacts form a Bardeen-Cooper-Schrieffer BCS energy gap which manifests as an increased contact resistance near B 0. The contact resistance .