Wafer Scale Synthesis of Thin Film Black Arsenic Phosphorus
Herein we report the wafer-scale synthesis of few-layered black arsenic phosphorus (b- AsP) alloys via two-step solid-source molecular beam deposition (MBD) and subsequent hermetic thermal annealing. We characterized our thin films with a variety of compositional and structural metrology techniques. X-ray photoelectron spectroscopy and energy dispersive spectroscopy determine compositions of As0.78P0.22 for our thin films, while x-ray reflectivity measurements indicate film thicknesses of 6-9 nm. High resolution transmission electron spectroscopy images reveal a nanocrystalline morphology with orthorhombic b-AsP grains on the order of ~ 5 nm. Raman scattering spectroscopy is employed to characterize the vibrational structure of our thin films, and results obtained from experiments are in excellent agreement with the b-AsP bulk crystal spectra. Evidence of conformal wafer-scale is substantiated by Raman mapping. We simulate crystal structure, bandgaps, and Raman spectra from first-principle DFT- based computations and find good agreement with our experimental results. This work is the first
demonstration of on-wafer synthesis of b-AsP. Our wafer-scale growth technique enables the development of next-generation b-AsP devices for optoelectronic, digital and RF applications.