Nanometer-Thick Metastable Zinc Blende γ-MnTe Single-Crystalline Films for High-Performance Ultraviolet and Broadband Photodetectors

Abstract

Van der Waals heteroepitaxial (vdWE) has been intensely developed and considered as the most promising heteroepitaxial technique for growth of high-quality nanoscale films, covalent-bonded semiconductor films, and heterostructures to create the next-generation flexible electronic/optoelectronic devices because of its nature of relief of the strict requirement of lattice matching and its elegant exfoliation and transfer to any substrates of interest. However, application of the vdWE route in growing metastable and artificial materials and structures is still absent. In this work, by using the molecular beam epitaxy (MBE), epitaxy of metastable γ-phase nanometer-thick MnTe thin films is achieved on two-dimensional mica substrates through attentive control of its growth kinetics. The good crystallinity of vdWE γ-MnTe thin films is shown by a low half peak width value of about 0.19° for 50 nm-thick epitaxial films. Moreover, a structure with perfect lattice, a wide E g opt of ∼3.26 eV with the direct electron transition structure, a broad absorption region from ultraviolet (UV) to near-infrared (NIR), and an ultrahigh absorption coefficient beyond 106 cm–1 in the UV region are found in vdWE nanometer-thick γ-MnTe thin films. The photodetectors with vdWE γ-MnTe/mica systems exhibit a highly sensitive broadband detecting from the UV to the NIR region. The detectors show an outstanding UV response with a high responsivity of 526 A W–1 and specific detectivity of 2.46 × 1012 Jones and show fast photoresponse speeds (τrising = 1.9 ms and τdecay = 1.7 ms) under a 375 nm laser illumination that indicate a great potential in flexible UV and broad spectrum detection of the photodetectors with vdWE nanometer-thick γ-MnTe/mica.

Layered ZnIn2S4 Single Crystals for Ultrasensitive and Wearable Photodetectors

“…[10,17,34] The optical bandgap can be interpolated using a Tauc relation (αhν) 2 = A(hν − E g ) for direct transition, where α is absorption coefficient and A is a constant characteristic for the material and hν is photon energy. [35] Using the absorption spectrum, Tauc plot is constructed in the inset in Figure 3c and the bandgap is determined to be E g = 2.38 eV, also consistent with the previous reports. [10,11,19] The optical properties were further investigated by room-temperature photoluminescence (PL) measurements using excitation laser with 405 nm wavelength.…”

Application of Transparent Fluorphlogopite Substrate in Flexible Electromagnetic Devices

“…The 2D functional films such as ReS 2 , [50][51][52][53] CdTe, [54,55] VS 2 , [56] MoS 2 , [57] MnTe, [58] CdSe, [59] HfS 2 , [60] WS 2 , [61] Bi 2 O 2 Se, [62][63][64][65][66][67][68] Bi 2 Se 3 , [67][68][69][70][71][72] Bi 4 Se 3 , [67] In 2 Se 3 , [73][74][75][76][77][78] Bi 2 Te 3 , [79,80] GaSe, [81] SnS, [82] Sb 2 Se 3 , [83] Sb 2 Te 3 , [84] Na 2 W 4 O 13 , [85] and Sb [86] have been deposited on fluorphlogopite substrate. Flexible devices made of 2D functional films grown on fluorphlogopite substrate like photodetectors, thermoelectric devices, ultra-thin and transparent flexible electrodes, etc., have shown great performance.…”

Polymorphic transformation from metastable β to stable α phase in MnTe flake

“…1) Among the various crystal structures, antiferromagnetic γ-MnTe with a wide gap (2.9 eV) has been widely investigated as a magnetic or optical material. [23][24][25] Moreover, methods to stabilize metastable β-MnTe have recently been explored, showing a wider bandgap (∼2.7 eV) and elevated resistivity (>1,000 Ω‧cm −1 ) in comparison to the renowned α phase. 26,27) In addition, recent theoretical simulations have estimated the piezoelectric coefficient and spontaneous electric polarization of β-MnTe.…”