Unintentionally doped (001)‐oriented orthorhombic κ‐Ga₂O₃ epitaxial films on c‐plane sapphire substrates are characterized by the presence of ≈ 10 nm wide columnar rotational domains that can severely inhibit in‐plane electronic conduction. Comparing the in‐ and out‐of‐plane resistance on well‐defined sample geometries, it is experimentally proved that the in‐plane resistivity is at least ten times higher than the out‐of‐plane one. The introduction of silane during metal‐organic vapor phase epitaxial growth not only allows for n‐type Si extrinsic doping, but also results in the increase of more than one order of magnitude in the domain size (up to ≈ 300 nm) and mobility (highest µ ≈ 10 cm²V⁻¹s⁻¹, with corresponding lowest ρ ≈ 0.2 Ωcm). To qualitatively compare the mean domain dimension in κ‐Ga₂O₃ epitaxial films, non‐destructive experimental procedures are provided based on X‐ray diffraction and Raman spectroscopy. The results of this study pave the way to significantly improved in‐plane conduction in κ‐Ga₂O₃ and its possible breakthrough in new generation electronics. The set of cross‐linked experimental techniques and corresponding interpretation here proposed can apply to a wide range of material systems that suffer/benefit from domain‐related functional properties.

Homogeneous films from SiO_1.3 (250 nm thick) were deposited on crystalline Si substrates by thermal evaporation of silicon monoxide. A part of the films was further annealed at 700 °C to grow amorphous Si (a-Si) nanoclusters in an oxide matrix, thus producing composite a-Si-SiO_1.8 films. Homogeneous as well as composite films were irradiated by 20-MeV electrons at fluences of 7.2 × 10¹⁴ and 1.44 × 10¹⁵ el/cm². The film thicknesses and optical constants were explored by spectroscopic ellipsometry. The development of the phase composition of the films caused by the electron-beam irradiation was studied by transmission electron microscopy. The ellipsometric and electron microscopy results have shown that the SiO_x films are optically homogeneous and the electron irradiation with a fluence of 7.2 × 10¹⁴ el/cm² has led to small changes in the optical constants and the formation of very small a-Si nanoclusters. The irradiation of the a-Si-SiO_x composite films caused a decrease in the effective refractive index and, at the same time, an increase in the refractive index of the oxide matrix. Irradiation induced increase in the optical band gap and decrease in the absorption coefficient of the thermally grown amorphous Si nanoclusters have also been observed. The obtained results are discussed in terms of the formation of small amorphous silicon nanoclusters in the homogeneous layers and electron irradiation induced reduction in the nanocluster size in the composite films. The conclusion for the nanoparticle size reduction is supported by infrared transmittance results.

The nucleation and growth of atomic layer deposited (ALD) vanadium oxide and sulfide layers were examined on the surface of sapphire and silicon. The growth of vanadium oxide was layer by layer on sapphire, but islandlike on silicon. The stable growth rates could be derived from the steric hindrance of the precursor molecules. The nucleation of vanadium sulfide was always islandlike. The merging of the islands, and, thus, continuous film growth, could be achieved by enhancing the surface active sites by chemical pretreatments, as well as by starting the ALD growth by longer cycles. With the combination of these approaches, ultrathin continuous VO2 and VS layers could be grown. The nucleation was also modeled mathematically, and the unknown starting boundary conditions could be derived from the model fitting.

Antimony selenide (Sb₂Se₃) is an Earth-abundant and non-toxic material that stands out as a promising absorber for the fabrication of thin film solar cells. Despite significant advancements in recent years, all the devices reported in the literature exhibit open-circuit voltages well below the theoretical value. Identifying the factors contributing to this low voltage is an essential step for increasing the efficiency beyond the recently attained 10% milestone and moving closer to the theoretical limit. In this paper, we present the results of an in-depth analysis of a Sb₂Se₃ solar cell in the common superstrate configuration. By making use of current density–voltage characteristic as a function of both temperature and wavelength, capacitance–voltage measurements, and admittance spectroscopy, we ascribe the low open-circuit voltage to the presence of a potential barrier within the absorber material near the junction interface Furthermore, it was observed that the junction behavior in the dark and under illumination changes, which is compatible with the presence of deep electronic levels connected with intrinsic point defects.