Band Structure and Photoelectric Characterization of GeSe Monolayers

Abstract

Germanium selenide monolayer is promising in photoelectric applications for its natural p-type semiconductor and complicated band structures. Basic experimental investigations of few-to-monolayer germanium selenide are still absent; major scientific challenge is to develop of techniques for controllably thinned monolayers. In this study laser thinned monolayer germanium selenide on SiO 2 /Si substrates is demonstrated. A broad photoluminescence spectrum with eight continues peaks is observed from visible to infrared wavebands centered at ≈589, 655, 737, 830, 1034, 1178, 1314, and 1456 nm, respectively. First-principle calculations based on density functional theory illuminate the band structures of few-to-monolayer germanium selenide. Photoluminescence investigation combined with first-principle calculations indicates that the indirect to direct bandgap transition happens at few layers of N = 3. Current-voltage and photoresponse characteristics of monolayer based devices show 3.3 times the photosensitivity and much faster falling edges compared with those of the pristine nanosheet based devices. The present results provide useful insight into deep understanding of thickness dependent performances of germanium selenide monocrystalline.

GeSe nanosheets modified surface plasmon resonance sensors for enhancing sensitivity

“…The excitation source wavelength of the Raman microscope is 532 nm. The excitation peaks B 3g and A g 3 of the two different modes correspond to 151 cm −1 and 188 cm −1 , respectively, which is consistent with previous studies [1,33]. A scanning electron microscope (SEM) image of GeSe nanosheets overlying a gold film is presented in Figure 4, depicting the surface topography of the spin-coating layered material over the gold film and the GeSe thickness in the cross-sectional direction.…”

“…The optical constants of BK7 Dove prism, Cr, and Au can be obtained from the experimental measurement [29][30][31]. The optical constants of GeSe monolayer are given in references [32,33]. For calculating the reflection intensity of the TM-polarized light of the configuration, we employed the N-layer transfer matrix method [34].…”

In‐Plane Optical Anisotropy of Low‐Symmetry 2D GeSe

“…As an isostructural analogue of BP, GeSe also possesses the unique in‐plane anisotropic crystal structure stemmed from its puckered atom structure with two nonequivalent in‐plane crystal directions: armchair and zigzag . With a suitable bandgap (1.14 eV), high absorption coefficient (>10 5 cm −1 ), and high carrier mobility (128.6 cm 2 V −1 s −1 ), GeSe has demonstrated a promising potential in thin‐film solar cells and exhibited an efficiency of 1.48% with good stability .…”

Tuning the Optical Absorption Property of GeSe Thin Films by Annealing Treatment

“…Fortunately, there have been several reports about the bandgap tuning of GeSe through compositional modulation, such as alloying with Sn to form ternary Ge x Sn 1−x Se (0 ≤ x ≤ 1) alloy, showing continuously tunable bandgaps in the range of 0.87–1.13 eV . However, there are few reports available concerning the ability to tune the bandgap of GeSe in experiment through quantum confinement, despite the fact that ab initio calculations have predicted a blue shift of bandgap in GeSe nanosheets would occur when decreasing the thickness of nanosheets due to the quantum confinement . Therefore, it is highly desirable to explore a strategy of quantum confinement to modulate the bandgap of GeSe.…”