Weak localization and correlation effects in thin-film degenerate n-type silicon

Abstract

The magnetoconductance of thin-film n-type silicon has been studied in order to provide insight into the low-temperature behavior of recent silicon-based semiconductor-metal hybrid structures. There is considerable interest in such structures as potential candidates for creating nonmagnetic read-head sensors for ultrahigh-density recording. The magnetoconductance of thin-film silicon was therefore analyzed as a function of magnetic field orientation at temperatures ranging from T=4.2 to 300 K. At low temperatures, the magnetoconductance consists of two components that are attributed to weak localization and correlation effects. Surprisingly, the thin-film transport properties behave two-dimensionally for the localization contribution, whereas the correlation contribution is isotropic. Similar two-dimensional localization behavior has previously been reported for silicon inversion layers but was not expected for silicon systems with a finite thickness. An analysis of the magnetoconductance as a function of magnetic field orientation has verified that the localization contribution depends only on the perpendicular to plane component of the field. The Hall coefficient was observed to vary with magnetic field, providing further evidence for a magnetoconductance governed by electron-electron interactions. Fitting of the data at T=4.2 K and for low magnetic fields provided values for the localization parameter α, the inelastic scattering time τi, and the two-dimensional effective electron screening constant F̃σ.

Nature of electrons from oxygen vacancies and polar catastrophe at LaAlO3/SrTiO3 interfaces

“…It is worthy noticing that the negative MR in our samples persists up to 9 T from 50 K to 30 K, which indicated that the weak localization effect persists up to the magnetic field of 9 T. This result agrees with some typical low-dimensional conduction systems [17,40,41]. However, in some other lowdimensional conduction systems [42,43], the MR is negative for moderate magnetic field, followed by a positive MR at higher magnetic field, which indicated that some other effect like regular orbital scattering may become more important at higher magnetic field. The dominating factors for the difference in low-dimensional conduction systems need to be further investigated.…”

Electron-electron interaction correction and magnetoresistance in tilted fields in Si-based two-dimensional systems

“…5 that show a factor of 3 diminished magnetoresistance in almost the same parallel field), and is not very probable because of thin potential well in Si-MOSFETs (∼ 3nm) compared to magnetic length l B [nm]= 25.7(B || [T]) −0.5 ; (ii) mobility may depend on Zeeman splitting in agreement with the predictions of the screening theory [27][28][29]. The latter mechanism should produce direction-independent positive magnetoresistance, exactly the behavior observed in heavilydoped multisubband thin Si quantum wells [64]. This however does not reconcile with our data.…”

Spin transport and Hanle effect in silicon nanowires using graphene tunnel barriers

“…No evidence of an inverted Hanle signal is observed, providing further evidence that the graphene layer has a smoothing effect that reduces interface roughness of the NiFe injector and thus minimizes accompanying fringe fields. Control samples using non-magnetic contacts show small positive magnetoresistance consistent with a Lorentzian type of magnetoresistance, ruling out weak localization, which might be more prevalent for these lower dimensional samples 58,59 . Both the amplitude (550 O) and linewidth are much larger than those of corresponding data obtained from NW samples which showed NLSV signals (Figs 3d and 4d).…”