Transport properties of partially equilibrated quantum wires

We study the effect of thermal equilibration on the transport properties of a weakly interacting one-dimensional electron system. Although equilibration is severely suppressed due to phase-space restrictions and conservation laws, it can lead to intriguing signatures in partially equilibrated quantum wires. We consider an ideal homogeneous quantum wire. We find a finite temperature correction to the quantized conductance, which for a short wire scales with its length, but saturates to a length-independent value once the wire becomes exponentially long. We also discuss thermoelectric properties of long quantum wires. We show that the uniform quantum wire is a perfect thermoelectric refrigerator, approaching Carnot efficiency with increasing wire length.Comment: 20 pages, 6 figure

Resistivity of inhomogeneous quantum wires

We study the effect of electron-electron interactions on the transport in an inhomogeneous quantum wire. We show that contrary to the well-known Luttinger liquid result, non-uniform interactions contribute substantially to the resistance of the wire. In the regime of weakly interacting electrons and moderately low temperatures we find a linear in T resistivity induced by the interactions. We then use the bosonization technique to generalize this result to the case of arbitrarily strong interactions.Comment: 4 pages, 1 figur

Imprinted Nanostructures for Light Management in Crystalline Silicon Thin Film Solar Cells on Glass

We present various imprinted nanostructures for light management in liquid phase crystallized silicon thin film solar cells enabling both, increased jsc by enhanced absorption and excellent electronic material quality with Voc values above 640 m

Conductance of fully equilibrated quantum wires

We study the conductance of a quantum wire in the presence of weak electron-electron scattering. In a sufficiently long wire the scattering leads to full equilibration of the electron distribution function in the frame moving with the electric current. At non-zero temperature this equilibrium distribution differs from the one supplied by the leads. As a result the contact resistance increases, and the quantized conductance of the wire acquires a quadratic in temperature correction. The magnitude of the correction is found by analysis of the conservation laws of the system and does not depend on the details of the interaction mechanism responsible for equilibration.Comment: 4 pages, 2 figure

Valence band offset and hole transport across a SiOx 0 lt;x lt;2 passivation layers in silicon heterojunction solar cells

In this work, the valence band offset amp; 916;EV and hole transport across the heterojunction between amorphous silicon suboxides a SiOx H and crystalline silicon c Si is investigated. Thin layers ranging from pure intrinsic a Si H to near stoichiometric a SiO2 were grown by varying precursor gas mixtures during chemical vapor deposition. A continuous increase of amp; 916;EV starting from amp; 8776; 0 .3 eV for the a Si H c Si to gt; 4 eV for the a SiO2 c Si heterointerface was measured by in system photoelectron spectroscopy. Furthermore, p a Si H i a SiOx H n c Si i,n a Si H heterojunction solar cells, with intrinsic a SiOx H passivation layers deposited using the same parameter sets, were fabricated. We report a linear decrease of the solar cell fill factor for increasing amp; 916;EV in the range of 0.27 0.85 eV. The reason is an increase of the barrier height for holes at the i a SiOx H n c Si heterojunction and a simultaneous change of the hole transport mechanism from thermionic emission to defect assisted tunnel hopping through valence band tail states. It is demonstrated that as compared to a single layer, significantly larger barrier heights can be tolerated in a stack of high band gap material and a material with lower band gap, forming a staircase of band offsets. This could allow the application of these layers in silicon heterojunction solar cell

Valence band offset in heterojunctions between crystalline silicon and amorphous silicon sub oxides a SiOx H, 0 lt;x lt;2

The heterojunction between amorphous silicon sub oxides a SiOx H, 0 amp; 8201; lt; amp; 8201;x amp; 8201; lt; amp; 8201;2 and crystalline silicon c Si is investigated. We combine chemical vapor deposition with in system photoelectron spectroscopy in order to determine the valence band offset amp; 916;EV and the interface defect density, being technologically important junction parameters. amp; 916;EV increases from amp; 8776;0.3 amp; 8201;eV for the a Si H c Si interface to gt;4 amp; 8201;eV for the a SiO2 c Si interface, while the electronic quality of the heterointerface deteriorates. High bandgap a SiOx H is therefore unsuitable for the hole contact in heterojunction solar cells, due to electronic transport hindrance resulting from the large amp; 916;EV. Our method is readily applicable to other heterojunction

Colored delta-T noise in Fractional Quantum Hall liquids

Photons are emitted or absorbed by a nano-circuit under both equilibrium and non-equilibrium situations. Here, we focus on the non-equilibrium situation arising due to a temperature difference between the leads of a quantum point contact, and study the finite frequency (colored) noise. We explore this delta-$T$ noise in the finite frequency regime for two systems: conventional conductors described by Fermi liquid scattering theory and the fractional quantum Hall system at Laughlin filling fractions, described by the chiral Luttinger liquid formalism. We study the emission noise, its expansion in the temperature difference (focusing on the quadratic component) as well as the excess emission noise defined with respect to a properly chosen equilibrium situation. The behavior of these quantities are markedly different for the fractional quantum Hall system compared to Fermi liquids, signalling the role of strong correlations. We briefly treat the strong backscattering regime of the fractional quantum Hall liquid, where a behavior closer to the Fermi liquid case is observed

Electronic transport in inhomogeneous quantum wires

We study the transport properties of a long non-uniform quantum wire where the electron-electron interactions and the density vary smoothly at large length scales. We show that these inhomogeneities lead to a finite resistivity of the wire, due to a weak violation of momentum conservation in the collisions between electrons. Estimating the rate of change of momentum associated with non-momentum-conserving scattering processes, we derive the expression for the resistivity of the wire in the regime of weakly interacting electrons and find a contribution linear in temperature for a broad range of temperatures below the Fermi energy. By estimating the energy dissipated throughout the wire by low-energy excitations, we then develop a different method for deriving the resistivity of the wire, which can be combined with the bosonization formalism. This allows us to compare our results with previous works relying on an extension of the Tomonaga-Luttinger model to inhomogeneous systems.Comment: 18 pages, 2 figures. Invited paper for special issue of Journal of Physics: Condensed Matter on "The 0.7 Feature and Interactions in One-dimensional Systems