II. EXPERIMENTAL DETAILS A. Synthesis of Ag NWsSynthesis of Ag NWs has been carried out by various procedures, such as template based 14,15 and soft solution methods. 16,17 Here, the Ag NWs were synthesized by reducing silver nitrate (AgNO 3 ) with ethylene glycol (EG) in presence of copper dichloride dihydrate (CuCl 2 + 2 H 2 O) and polyvinylpyrrolidone (PVP). The EG is used as solvent and reducing agent whereas the PVP is used as capping agent. 18 In the beginning, 10 mL of EG (Sigma-Aldrich, anhydrous 99.8 %) was heated in an oil bath at 151.5 ○ C for 1 h under continuous magnetic stirring at 260 rpm. Then, 80 µL of a 4 mM CuCl 2 + 2 H 2 O (Sigma-Aldrich, 99.999 %)/EG solution was added to the preheated EG and stirred for another 15 min. Next, 3 mL of 0.282 mM PVP (Sigma-arXiv:1410

Abstract. For β-Ga 2 O 3 only little information exist concerning the thermal properties, especially the thermal conductivity λ. Here, the thermal conductivity is measured by applying the electrical 3ω-method on Czochralski-grown β-Ga 2 O 3 bulk crystals, which have a thickness of 200 µm and 800 µm. At room temperature the thermal conductivity along the [100]-direction in Mg-doped electrical insulating and undoped semiconducting β-Ga 2 O 3 is confirmed as 13 ± 1 Wm −1 K −1 for both crystals. The thermal conductivity increases for decreasing temperature down to 25 K to λ(25 K) = (5.3±0.6)·102 Wm −1 K −1 . The phonon contribution of λ dominates over the electron contribution below room temperature. The observed function λ(T ) is in accord with phonon-phonon-Umklapp scattering and the Debye-model for the specific heat at T 90 K which is about 0

Intragrain charge carrier mobilities measured by time-resolved terahertz spectroscopy in state of the art Cu2ZnSn(S,Se)4 kesterite thin films are found to increase from 32 to 140 cm2 V−1 s−1 with increasing Se content. The mobilities are limited by carrier localization on the nanometer-scale, which takes place within the first 2 ps after carrier excitation. The localization strength obtained from the Drude-Smith model is found to be independent of the excited photocarrier density. This is in accordance with bandgap fluctuations as a cause of the localized transport. Charge carrier localization is a general issue in the probed kesterite thin films, which were deposited by coevaporation, colloidal inks, and sputtering followed by annealing with varying Se/S contents and yield 4.9%–10.0% efficiency in the completed device.

Thermoelectric (TE) properties of a single nanowire (NW) are investigated in a microlab which allows the determination of the Seebeck coefficient S and the conductivity σ. A significiant influence of the magnetization of a 70 nm ferromagnetic Ni-NW on its power factor S²σ is observed. We detected a strong magneto thermopower effect (MTP) of about 10% and an anisotropic magneto resistance (AMR) as a function of an external magnetic field B in the order of 1%. At T = 295 K and B = 0 T we determined the absolute value of S = -(19 ± 2) µV/K. At zero field the figure of merit ZT ≈ 0.02 was calculated using the Wiedemann-Franz-law for the thermal conductivity. The thermopower S increases considerably as a function of B up to 10% at B = 0.5 T, and with a magneto thermopower of ∂S/∂B ≈ -(3.8 ± 0,5) µV/(K . T). The AMR and MTP are related by ∂s/∂r ≈ -11 ± 1 (∂s = ∂S/S).The TE efficiency increases in a transversal magnetic field (B =0.5T) due to an enhanced power factor by nearly 20%.