Surface and Optoelectronic Properties of Ultrathin Trigonal Selenium: A Density Functional Theory Study with van der Waals Correction

Abstract

Selenium is an important earth-abundant and nontoxic semiconductor with numerous applications across semiconductor industries. Selenium has drawn attention from scientific communities for photovoltaics and imaging devices. Its usage as a photosensitive material largely involves the synthesis of the amorphous phase (a-Se) via various experimental techniques. However, the ground state crystalline phase of this material, the trigonal selenium (t-Se), a layered van der Waals solid, has not been extensively studied for its optimum electronic and optical properties. In this work, we present systematic studies based on density functional theory (DFT) for ultrathin (101̅ 0) surface slabs of t-Se. We report the surface energy as well as work function and electronic and optical properties as a function of number of layers for (101̅ 0) surface slabs to access its suitability for applications as a photosensitive material and compare these calculations to historical data.

Excellent ultraviolet optical limiting properties of Se nanosheets

“…Figure 3(b) is the x-ray diffraction pattern of Se powder. By means of the analysis of the diffraction peaks, we can determine that the crystalline phase structure is typical of the t-Se phase, which further proves the crystal structure of Se powder [30]. Figure 4(a) insert demonstrates the energy-dispersive x-ray spectroscopy image of Se powder.…”

“…t-Se is the most stable crystal structure with the highest anisotropy. It is a semiconducting solid, consisting of helical chains of covalently bound Se atoms and relatively weak van der Waals forces between the chains [27][28][29][30]. These provide the possibility for the preparation of Se nanosheets using the liquid phase exfoliation (LPE) method.…”

Formation and Characterization of MgSe Alloys by Pulsed Laser Welding Technique

“…The X‐ray diffraction (XRD) patterns for the samples under study are shown in Figure . The figure illustrates the standard reflections from monoclinic selenium ($$a = 12.85\;\hbox{\AA}, b = 8.07\;\hbox{\AA}, c = 9.13\;\hbox{\AA}$$, $$\beta = 93.31^{\rm o}$$ [ 10,11 ] ), trigonal selenium ($$a = b = 4.366\;\hbox{\AA}, c = 4.954\;\hbox{\AA}, \gamma = 120^{\rm o}$$ [ 12 ] ), and hexagonal Mg ($$a = 3.209\;\hbox{\AA}, c = 5.21\;\hbox{\AA}$$ [ 13 ] ). The X‐ray diffraction patterns for the MgSe pellets pressed at 100 bars before and after being welded with laser are also shown in Figure 3.…”

“…The X-ray diffraction (XRD) patterns for the samples under study are shown in Figure 3. The figure illustrates the standard reflections from monoclinic selenium (a = 12.85 Å, b = 8.07 Å, c = 9.13 Å, 𝛽 = 93.31 o [10,11] ), trigonal selenium (a = b = 4.366 Å, c = 4.954 Å, 𝛾 = 120 o [12] ), and hexagonal Mg (a = 3.209 Å, c = 5.21 Å [13] ). The X-ray diffraction patterns for the MgSe pellets pressed at 100 bars before and after being welded with laser are also shown in Figure 3.…”

Allotropy of selenium nanoparticles: Colourful transition, synthesis, and biotechnological applications

“…For instance, crystalline Se capping topological insulators (TI) showed improved capability to preserve the intrinsic transport properties of TI in comparison with amorphous Se (Lin et al, 2018 ). In addition, Barman et al ( 2022 ) recently observed high optical absorption coefficient and favourable transport properties of t‐Se ultrathin films, which make t‐Se attractive for the fabrication of photosensitive detector devices. Not only industrially, but also from an environmental point of view, crystalline Se has been described to be highly settleable and therefore more prone for separation/recovery than a‐Se (Lenz et al, 2009 ).…”