Electron scattering mechanisms in copper lines were investigated to understand the extendibility of copper interconnects when linewidth or thickness is less than the mean free path. Electron-beam lithography and a dual hard mask were used to produce interconnects with linewidths between 25 and 45 nm. Electron backscatter diffraction characterized grain structure. Temperature dependence of the line resistance determined resistivity, which was consistent with existing models for completely diffused surface scattering and line-edge roughness, with little contribution from grain boundary scattering. A simple analytical model was developed that describes resistivity from diffuse surface scattering and line-edge roughness.

Efficient charge transport is demonstrated in TiO2/PbS quantum dot solar cells where the PbS absorber (∼1.1 eV band gap) is deposited by dip coating and ethanedithiol ligand exchange, with power efficiencies above 3% at AM1.5. An increase in power efficiency occurs as the device temperature is lowered to 170 K, with a open-circuit voltage of 0.66 V, short-circuit current density of 28.6 mA/cm2 and fill factor of 42.4%. This remarkable temperature dependence is due to a large increase in charge transport between the PbS quantum dots with decreasing temperature.

Path integral Monte Carlo simulations are applied to study dense atomic hydrogen in the regime where the protons form a Wigner crystal. The interaction of the protons with the degenerate electron gas is modeled by Thomas-Fermi screening, which leads to a Yukawa potential for the proton-proton interaction. A numerical technique for the derivation of the corresponding action of the paths is described. For a fixed density of r s = 200, the melting is analyzed using the Lindemann ratio, the structure factor and free energy calculations. Anharmonic effects in the crystal vibrations are analyzed.

Thin film solar cells comprised of quantum-confined CdTe nanoparticles are shown to have a low intrinsic density of mid-gap trap states relative to their equivalent bulk film, indicating that the ligands are effective at electrically passivating surface states. Sintering the nanoparticles into a poly-crystalline thin film increases device performance but also increases the density of mid-gap trap states due to doping from the CdCl treatment and the formation of long range disorder such as grain boundaries and dislocations. Long term aging under illumination increases the density of mid-gap traps in the unsintered films due to degradation of the ligands.

A new data mining algorithm was developed to identify the strongest correlations between capacitance data (measured between -1.5 V and +0.49 V) and first -and second-level performance metrics (efficiency [η%], open-circuit voltage [V OC ], short-circuit current density [J SC ], and fill-factor [FF]) during the stress testing of voltage-stabilized CdS/CdTe devices. When considering only correlations between first-and second-level metrics, 96.5% of the observed variation in η% was attributed to FF. The overall decrease in V OC after 1,000 hours of open-circuit, light-soak stress at 60 ºC was about -1.5%. The most consistent correlation identified by the algorithm in this particular experiment between FF and third-level metric capacitance data during stress testing was between FF and hysteresis in the apparent CdTe acceptor density (N a ) between reverse and forward voltages scans, as determined in forward voltage bias. Since the contribution of back-contact capacitance to total capacitance increases with increasing positive voltage, this result suggests that degradation in FF was associated with decreases in N a hysteresis near the CdTe/back contact interface.