Hydrogen‐Assisted Growth of Ultrathin Te Flakes with Giant Gate‐Dependent Photoresponse

Abstract

Tellurium (Te), as an elementary material, has attracted intense attention due to its potentially novel properties. However, it is still a great challenge to realize high-quality 2D Te due to its helical chain structure. Here, ultrathin Te flakes (5 nm) are synthesized via hydrogen-assisted chemical vapor deposition method. The density functional theory calculations and experiments confirm the growth mechanism, which can be ascribed to the formation of volatile intermediates increasing vapor pressure of the source and promoting the reaction. Impressively, the Te flake-based transistor shows high on/off ratio ≈10 4 , ultralow off-state current ≈8 × 10 −13 A, as well as a negligible hysteresis due to reducing thermally activated defects at 80 K. Moreover, Te-flake-based phototransistor demonstrates giant gate-dependent photoresponse: when gate voltage varies from −70 to 70 V, I on /I off is increased by ≈40-fold. The hydrogen-assisted strategy may provide a new approach for synthesizing other high quality 2D elementary materials.

Synthesis Techniques, Optoelectronic Properties, and Broadband Photodetection of Thin‐Film Black Phosphorus

“…Besides, some other vdW layered materials are also explored for MIR photodetection applications, such as tellurium (Te), PtSe 2 , and PdSe 2 , which possess better chemical stability in ambient environment. [ 245–249 ] Te crystal is stacked together from individual helix molecular chains via van der Waals forces. [ 250,251 ] Therefore, the dangling‐bond‐induced recombination only occurs at the end of the chains in Te.…”

Novel two-dimensional monoelemental and ternary materials: growth, physics and application

“…After that, Te nanostructures based on other substrate such as sapphire, graphene/4H-SiC and HOPG have also be studied in recent years [137][138][139][140][141][142][143]. In general, there are many kinds of synthetic methods, including physical vapor deposition (PVD) [135], MBE [138], LPE [144][145][146], hydrothermal reaction [131,132,147,148], CVD [130] and thermal evaporation deposition [149,150]. Without consideration of the crystal scale, both Lin et al and Wu et al demonstrated free-standing exfoliated Te nanosheets at the size of several hundred nanometers in polarized solvent by ultrasonic bath and centrifugation [144,146].…”

“…Furthermore, in 2019, Zhang et al prepared triangular 2D Te flakes on mica substrate via a creative CVD, in the presence of TeO 2 with the mixture gas of Ar/H 2 . The thinnest thickness can reach approximately 5 nm (see Figure 4C-E) [130]. Freshly, Zhao et al developed a thermal deposition method at cryogenic temperature to receive large-area polycrystalline Te nanosheets, showing unprecedented FET performance [150].…”

“…The TI behavior found in 2D α-Te over the 3-nm region was determined by STM [148], already theoretical explained in strain engineering for Te nanowires and nanosheets [143,154,156]. For optical behavior, 2D Te with a thickness from 9.1 nm to 20.5 nm showed four red-shifted Raman peaks of 94 cm −1 (E 1 TO), 105 cm −1 (E 1 LO), 125 cm −1 (A 1 ) and 143 cm −1 (E 2 ), attributed to the augmentation of deformation potential in lattice orientation and the interlayer long-range Coulombic interactions [130,147]. Meanwhile, E 1 TO and E 1 LO Raman modes are shifted and disappeared for few-layered and multilayered 2D Te, respectively [147,157].…”

“…Given the various physics of 2D tellurium and tellurene, such as flexibility, stability, high mobility, narrow bandgap and high optical absorption, their applications in FETs [130,137,147,150], photodynamic therapy [144], optical modulator [146], polarized infrared imaging [132], quantum information [131,155], PDs [130,132,136] and solar absorber [159] have been explored in recent years. In 2018, Wu et al showed that thickness-dependent 2D Te FETs exhibited the recorded highest hole mobility of 700 cm 2 · V −1 · s −1 with a moderate on/off ratio of ~10 3 at ambient conditions.…”