Minigaps in strained silicon quantum wells on tilted substrates

Abstract

The two-dimensional electron gas formed at the inverted surface of a tilted silicon substrate shows unusual magnetotransport properties due to the presence of a minigap in the density of states. For metal–oxide–semiconductor inversion layers the strong scattering at the interface limits the mobility to values μ<10–20 000 cm2/V s. To achieve mobilities approaching 105 cm2/V s we have used strained Si:SiGe quantum wells grown on substrates tilted away from the (001) normal by 0°, 2°, 4°, 6°, and 10°. Their transport properties have been measured in the temperature range of 20–500 mK. All the samples show strong Shubnikov–de Haas oscillations. For the 2° and 4° samples the envelope of the fast oscillations is modulated by a longer period oscillation at low magnetic fields. We attribute the slow oscillation in the 2° and 4° samples to the presence of a minigap. For the 6° and 10° samples the minigap is higher than the Fermi energy and is not expected to influence the transport properties.

Thickness-dependent structural characteristics for a sputtering-deposited chromium monolayer and Cr/C and Cr/Sc multilayers

“…The second region has a very low growth exponent of 0.11 AE 0.02, which is attributed to the dominant effect of surface diffusion (Yu et al, 2008). Considering the deposition technology of low Ar pressure and T/T m < 0.3 where T is the deposition temperature on the substrate and T m the melting temperature of Cr, the microstructure of the Cr layer presents a columnar structure with void streaks, which are attributed to nucleation and coalescence (Thornton, 1986). In this region, the surface adhesive force is significantly stronger than the adatom cohesive force.…”

Conductance and persistent current in quasi-one-dimensional systems with grain boundaries: Effects of the strongly reflecting and columnar grains

“…Finally, we extend our study to the 3D conductors with the columnar grains [19][20][21][22][23][24][25][26][27][28], which are fundamentally different from the tiny randomly-oriented grains, implicitly assumed in any white-noise-based description of disorder. We show that the typical persistent current in the diffusive metallic ring with the columnar grains is given by the formula…”

P‐42: Effects of Deposition Temperature on the Etched Feature of Thin Chromium Film and Their Application to Field Emitter Arrays (FEAs)

“…2d). The tendency of the structures in these Cr films can be explained by zone model for the grain structure [9][10] . Based on the zone model of grain structure, the basic features of crystal properties were essentially independent of the substrate material and deposition rate and were strongly dependent of the T s .…”