Molecular beam epitaxy growth of thin films of SnS2 and SnSe2 on cleaved mica and the basal planes of single-crystal layered semiconductors: Reflection high-energy electron diffraction, low-energy electron diffraction, photoemission, and scanning tunneling microscopy/atomic force microscopy characterization

Abstract

SnS2 and SnSe2 thin films were deposited by molecular beam epitaxy (MBE) methods on a variety of layered semiconductor substrates (freshly cleaved SnS2, SnSe2, WSe2, MoS2, MoTe2, GaSe, InSe) and cleaved mica, for investigation of the interfaces formed as a result of MBE growth. These ultrathin films were characterized in situ by x-ray photoelectron spectroscopy and surface reflection high energy and low energy electron diffraction techniques. The growth modes were verified ex situ by scanning tunneling microscopy and/or atomic force microscopy [scanning probe microscopies (SPM)]. Despite the chemical and structural similarities between SnS2 and SnSe2, SPM measurements show that the two materials as ultrathin films have different growth morphologies in the first few monolayers. Photoelectron spectroscopy (PES) measurements lead to the conclusion that both materials grow on the basal planes of most layered substrates in an epitaxial, layer-by-layer mode. Small deviations from ideal Frank–van der Merwe growth for these thin films could be determined from PES intensity ratios versus coverage. Deposition of both materials on freshly cleaved mica, where the lattice mismatch between the substrate and the overlayer surface unit cell dimension exceeds 40%, yields exclusively 500–1000 Å diameter epitaxial islands with threefold symmetry.

Structural and photoemission investigations of a new pseudo binary semimagnetic semiconductor: Sn1−xMnxSe2

“…To our knowledge, the literature does not mention a binding energy numerical value that can be compared with the Sn 3d binding energy measured in this study. The only photoemission related publications devoted to SnSe 2 are concerned with the characterization of the valence band [25], the band structure [26] and the growth mode of the layered semiconductor [27,28]. Nevertheless, based on the work of Schlaf et al [27,28], one can estimate from a picture (with 0.1 eV accuracy) the Sn 3d a very good agreement is observed between these results and our first data.…”

Large Single Crystal SnS2 Flakes Synthesized from Coevaporation of Sn and S

“…32 Only one hexagonal pattern was seen on a phosphor screen due to the normal incidence of the electrons on the mica surface in LEED. In our RHEED patterns, many higher order hkil spots within the hexagonal symmetry were seen because the wave vector k for 15 keV in RHEED is one order of magnitude longer than k for 150 eV in LEED (k (Å -1 ) = 2π ට ாሺሻ ଵହ.ସ ).…”

A roadmap for electronic grade 2D materials

“…• Experimental control over nucleation and layer number of 2D films • Computational representation of complex synthesis environments & corresponding impact on 2D material nucleation and growth Substrate defects, like step-edges formed during annealing, surface vacancies or pits, also enhance nucleation and the growth rate, which promotes undesirable vertical growth. Epilayer-substrate interactions have also been observed through substrate defects, 138,140 and some preliminary evidence suggests chalcogen scavenging from a TMD or topological insulator substrate. 105 To aid in efforts to control nucleation and layer growth, theoretical studies can be performed.…”