Synthesis and photoluminescence of high density GeSe triangular nanoplate arrays on Si substrates

Abstract

We have grown germanium selenide (GeSe) triangular nanoplate arrays (TNAs) with a high density (3.82 × 10 6 / mm 2 ) on the Si (111) substrate using a simple thermal evaporation method. The thickness and trilateral lengths of a single triangular nanoplate were statistically estimated by atomic force microscopy (AFM) as 44 nm, 365 nm, 458 nm and 605 nm, respectively. Transmission electron microscopy (TEM) images and Xray diffraction (XRD) patterns show that the TNAs were composed of single crystalline GeSe phase. The Se-related defects in the lattice were also revealed by TEM images and Raman vibration modes. Unlike previously reported GeSe compounds, the GeSe TNAs exhibited temperature-dependent photoluminescence (PL). In addition, not previously reported PL peak (1.25 eV) of the 44 nm thick TNAs at 5 K was in the gaps between those of GeSe monolayers (1.5 nm) and thin films (400 nm), revealing a close relationship between the PL peak and the thickness of GeSe. The high-density structure and temperature-dependent PL of the TNAs on the Si substrate may be useful for temperature controllable semiconductor nanodevices.

Free-standing large, ultrathin germanium selenide van der Waals ribbons by combined vapor–liquid–solid growth and edge attachment

“…24 Indeed, recent electrical measurements on GeSe single crystals have suggested a relatively large acceptor activation energy of 37.8 meV, 37 in good agreement with our STEM-CL results. Overall, by showing strong luminescence over the entire temperature range from 100 K to room temperature – in contrast to other studies that did not detect luminescence close to room temperature 26 – our spectroscopy results on single GeSe nanoribbons confirm the formation of high-quality single crystals with low concentration of defects acting as non-radiative recombination centers. These findings are promising for potential applications of our large-area nanoribbons, for example in photovoltaics.…”

“…18 Vapor transport growth of GeSe flakes should be straightforward since GeSe evaporates as a molecule and has high vapor pressure at relatively low temperatures, similar to other group IV-monochalcogenides, which has allowed the controlled synthesis of GeS 19 and SnS flakes 20,21 as well as heterostructures between them 22,23 under mild conditions. However, vapor transport growth using stoichiometric GeSe as a precursor has been carried out mostly at high source temperatures (T S ) with mixed results to date, including the formation of massive nano-combs (T S = 570 °C), 24,25 sub-μm triangular plates with tens of nm thickness (470 °C), 26 standing hexagonal plates with ∼15 nm thickness and lateral sizes of a few μm (550 °C), 2 and ribbons of a hexagonal GeSe polymorph (550 °C). 27 Recent attempts to reduce the thermal budget of the vapor source (T S = 430 °C) yielded complete films consisting of standing grains on SiO 2 .…”

Structure-dependent high-TC ferromagnetism in Mn-doped GeSe

“…29,30 Another small peak at 175.2 cm −1 exists in all the samples, which is corresponding to the A g 2 vibrational mode related to V Ge s in GeSe. 31 In addition, the peak at 258.7 cm −1 , which is attributed to the phonon vibrations of V Ge -induced Se chains and Ge–Se bonds, 32–34 dramatically decreases or even disappears after Mn doping, indicating that V Ge s are mainly occupied by Mn dopants. The chemical valences of the elements in the samples are investigated by XPS.…”

Phase-Specific Vapor–Liquid–Solid Growth of GeSe and GeSe2 van der Waals Nanoribbons and Formation of GeSe–GeSe2 Heterostructures

“…The luminescence of the GeSe–GeSe 2 heterostructure is significantly enhanced, with a ∼1.7-fold increase in the intensity of the band-edge peak. This finding shows that GeSe 2 termination is effective in suppressing nonradiative surface recombination in GeSe, which is responsible for its low luminescence intensity at room temperature . We note the presence of a higher-energy emission at ∼2 eV photon energy for both as-grown and selenized GeSe ribbons (Figure g).…”

“…This finding shows that GeSe 2 termination is effective in suppressing nonradiative surface recombination in GeSe, which is responsible for its low luminescence intensity at room temperature. 41 We note the presence of a higher-energy emission at ∼2 eV photon energy for both as-grown and selenized GeSe ribbons (Figure 4g). Such transitions at energies well above the fundamental band gap are frequently observed in CL, 42 but their precise origin tends to be difficult to ascertain.…”