GaN films grown on (0 0 1) and (1 1 0) MgF2 substrates by plasma-assisted molecular beam epitaxy (PA-MBE)

Microstructural analysis of GaN films grown on (1 0 0) MgF$_2$ substrate by 4D nanobeam diffraction and energy-dispersive X-ray spectrometry

“…much smaller compared to the 525°C samples. Furthermore, in-diffusion of Mg and F from the substrate into the GaN layer is evidenced by EDX in agreement with previously reported SIMS data [5].…”

“…For PA-MBE at 525 • C we observe αand β-GaN with growth directions of [110] and [0001] parallel to the [100] MgF 2 substrate orientation, which is fully consistent with previously published XRD data [5,8,9]. Both variants exhibit grain sizes in the 100-200 nm range with no preferred nucleation of either phase.…”

“…For such applications, GaN has to be combined with window materials, which are highly transparent in the deep UV. Typical substrate materials such as sapphire, silicon, GaAs, ZnO 6H-SiC do not meet this requirement, while research on III-nitride growth on suitable window materials has just recently been initiated [5]. The authors studied MgF 2 , which fulfills the optical constraints and has successfully been used as substrate for metal oxides such as TiO 2 [6] and VO 2 [7].…”

“…The authors studied MgF 2 , which fulfills the optical constraints and has successfully been used as substrate for metal oxides such as TiO 2 [6] and VO 2 [7]. In fact, epitaxial growth of mainly cubic GaN (β-GaN) in [111] and [110] orientation has been reported recently for Ga-rich growth conditions in plasma-assisted molecular beam epitaxy (PA-MBE) [5] as studied by x-ray diffraction (XRD). Further studies [8,9] provided evidence that depending on the growth temperature a mixture of metastable β-GaN and thermodynamically stable α-GaN forms with the hexagonal phase dominating at higher growth temperature (700 • C).…”

Digital Tuning of the Transition Temperature of Epitaxial VO2 Thin Films on MgF2 Substrates by Strain Engineering

“…This is due to reduced V mobility which prevents the formation of a smooth and continuous film. [36,37] This poor nucleation of the (001)-oriented VO 2 crystallites, particularly for the 250 °C film, is in agreement with the Volmer-Weber growth mode observed via RHEED (Figure 1). Increasing the growth temperature to 300 °C promotes coalescence of the crystallites which improves the overall MIT.…”