The influence of Ga⁺irradiation on the transport properties of mesoscopic conducting thin films

Abstract

Abstract. We studied the influence of 30 keV Ga + -ions -commonly used in focused ion beam (FIB) devices -on the transport properties of thin crystalline graphite flake, La 0.7 Ca 0.3 MnO 3 and Co thin films. The changes of the electrical resistance were measured in-situ during irradiation and also the temperature and magnetic field dependence before and after irradiation. Our results show that the transport properties of these materials strongly change at Ga + fluences much below those used for patterning and ion beam induced deposition (IBID), limiting seriously the use of FIB when the intrinsic properties of the materials of interest are of importance. We present a method that can be used to protect the sample as well as to produce selectively irradiation-induced changes.

Influence of interfaces on the transport properties of graphite revealed by nanometer thickness reduction

“…the sample-dependent distance between interfaces along the c−axis of the graphite structure, it is appealing to argue that metalliclike interfaces are the origin for the SdH oscillations. In a different experiment the SdH oscillations were enhanced notably by ion irradiation of a 15 nm thick graphite flake, which hardly showed SdH oscillations before irradiation [28,34]. These early experiments clearly suggest that the SdH oscillations are not intrinsic of the ideal graphite structure but they are related to defective regions in the graphite sample.…”

Josephson-coupled superconducting regions embedded at the interfaces of highly oriented pyrolytic graphite

“…Energy dispersive x-ray spectroscopy (EDAX) measurements were made to check for the sample impurities revealing a concentration of ∼2% of Ga in that surface near region. Independently done studies of the change in transport properties of thin graphite flakes after Ga + irradiation showed that the metallic-like behavior is destroyed and a large increase in electrical resistance is observed already at much lower Ga + fluences [30].…”

“…The four-contact method used to measure the voltage response allows us to obtain the contribution of the inner part of the lamellae, i.e. of the nonmodified region because its resistance with its interfaces is much smaller than the irradiated layer [30].…”

Evidence for semiconducting behavior with a narrow band gap of Bernal graphite

“…[31], in comparison with the rather weak 6 amplitudes, if observed at all, found nowadays in better quality samples or thin enough graphite samples. A clear demonstration that these SdH oscillations are actually non-intrinsic to ideal graphite is given by their appearance in thin graphite samples upon introducing defects by irradiation as shown in [15,32].…”