The properties of biaxially textured semiconductor films deposited on nanostructured buffer layers with biaxial texture closely approximate the physical properties of single-crystal. This near single-crystal film can serve as substrates and offer significant cost saving benefits in applications such as displays and photovoltaic devices. This thesis provides results of the growth and characterization of Ge films nanoepitaxially deposited onto biaxially textured Ge (homo) and CaF₂ (hetero) buffer layers. The film growth method was physical vapor deposition at normal and oblique angles of incidence. The characterization techniques used included atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray pole figure analyses.

The Ge films nanoheteroepitaxialy deposited on CaF₂ buffer layers were studied as a function of substrate temperature, the CaF₂ morphology and orientation ([001] and [110]) to see the influence of these variables on the Ge films. Ge films deposited at 400°C on [001] oriented CaF₂ buffer layer with ridge-like features resulted in nearly single-crystal Ge films of [001] orientation with 1.68° ± 1° in-plane dispersion and a 1:1 main pole to twin pole ratio. Ge films deposited at 400°C onto a [110] oriented CaF₂ buffer nanorods layer was found that the [110] Ge film has ∼20° in-plane dispersion but higher 6:1 twin ratio. The increased dispersion (∼20°) was attributed to the large dispersion in the CaF₂ buffer layer that resulted from the low vapor incidence angle used during its deposition. The difference in the twin ratio of the Ge films was attributed to the difference in substrate morphology. The [110] oriented CaF₂ buffer layer was composed of isolated nanorods while the [001] oriented CaF₂ buffer layer had micron long well ordered ridge structures. According to the theory of nanoepitaxy the isolated nanorods in the [110] oriented buffer layer provided more strain relief to the Ge epilayer. This reduced the number of dislocations in the film resulting in a lower relative intensity of the twin poles (or higher main pole to twin pole ratio).

The Ge films nanohomoepitaxialy deposited on Ge buffer layers on hydrogen terminated Si(100) were studied as a function of substrate temperature and deposition rate. In both the substrate temperature and deposition rate study the Ge buffer layer deposited at incident angle α=87°, temperature T=330°C, and rate=1.6 nm/min had {001}<110> biaxial texture with the lowest in-plane dispersion (0.92° ± 0.01°) and lowest relative intensity of twin poles (20:1). Ge films deposited on this buffer layer at 400°C had the lowest in-plane dispersion (0.83°), and a twin poles ratio (6:1). Ge films deposited directly on hydrogen terminated Si(100) at 400°C without Ge buffer layer had in-plane dispersion (0.47°) and twin ratio (1:1). The reduction in the relative intensity of the twin poles in the film deposited on the biaxial Ge buffer layer over the film deposited directly on H-Si(001) that has 4.2% Ge to Si lattice mismatch is attributed to the theory of strain relief in nanoepitaxy. The reduced dispersion and improved twin ratio in Ge films deposited on Ge buffer layer as compared to the nanoheteroepitaxial deposition of Ge on the [001] oriented CaF₂ buffer layers indicated that the homoepitaxial deposition of Ge films on biaxially textured Ge buffer layers resulted in a better quality Ge film that is nearly single-crystal with twinning.