Hydrogen‐Assisted Synthesis of Large‐Size 2D Bismuth Telluride Flakes for Broadband Photodetection up to 2 µm

Abstract

remote sensing, military reconnaissance, and medical examination. [2] Recently, photo detectors based on 2D materials and their heterostructures have attracted more and more attention. Thanks to diverse electronic band structures, 2D materials can cover a wide spectral range from ultraviolet-visible-infrared (IR)-terahertz (TH) frequencies. [3] Typical 2D materials include graphene, black phosphorous (BP), and transition metal dichalcogenides (TMDCs). Unfortunately, graphene photodetectors are limited due to the unavoidable large dark current caused by zero band gap and low absorption. [4] TMDCs (MX 2 , M = Mo, W, X = S, Se) are only limited to the visible band due to their wide bandgap (1-2.5 eV). [5] Black phosphorus (BP) has outstanding photodetection properties in the mid-infrared band and ultrahigh mobility (1000 cm 2 V −1 s −1 at room temperature). However, the instability of BP seriously limits its synthesis and application. [6] Therefore, it is urgent to develop new materials with suitable bandgap, high mobility, and air stability for broadband photodetection.Topological insulators have metallic Dirac-like surface states and insulating bulk states. The unique structure offers attractive features such as wide spectral absorption and layerdependent surface band structure, [7] which is beneficial to its application in broadband photodetection. Some topological insulator-based photodetectors have shown excellent optoelectronic performance in the visible-IR-THz band. [1a,3d,8] Among various 2D topological materials, Bi 2 Te 3 has a suitable band gap (0.16-1.36 eV), ultra-high mobility, and excellent air stability. [9] These outstanding properties enable Bi 2 Te 3 to be a promising candidate for high-performance broadband photodetectors. [8b,9c,10] However, further development of Bi 2 Te 3 -based photodetectors is limited by the fact that Bi 2 Te 3 single flakes are currently only available with a lateral size of up to few tens of micrometers. Up to now, there are various methods for synthesizing Bi 2 Te 3 , including mechanical exfoliation, [9a] molecular beam epitaxy (MBE), [11] liquid phase synthesis, [9c,10b,12] and chemical vapor deposition (CVD). [8b,13] Mechanical exfoliation is only suitable for proof-of-concept because of its low yield and tiny size. [9a] Although high-quality and large-scale Bi 2 Te 3 single crystals can be obtained by MBE, the technique still suffers from high cost, long time consuming (growth rate is Broadband photodetection including optical communication wavelength band is of great significance because of the great potential for various civilian and military applications. Topological insulators with unique surface electronic states have attracted more and more attention in broadband photo detection. Among them, due to its suitable band gap (0.16-1.36 eV), ultra-high mobility, and excellent air stability, 2D bismuth telluride (Bi 2 Te 3 ) is regarded as a promising candidate. However, the growth of large-size Bi 2 Te 3 is challenging because of the poor chemical reactivit...

Mixed-Dimensional PtSe2/Bi2Te3/Pyramid Si Heterojunction with a Light-Trapping Structure for Highly Sensitive Ultrabroadband Photodetection

“…Bi 2 Te 3 has a layered structure with a rhombohedral system of D 3 d ( R 3 m ) space group, as depicted in Figure a. A single Bi 2 Te 3 layer consists of five alternating atoms in order of Te–Bi–Te–Bi–Te .…”

Topological Insulator Bi2Se3 Heterojunction with a Low Dark Current for Midwave Infrared Photodetection

“…The device structure is shown in Figure 1a, which is a vertical heterojunction composed of multilayer Bi 2 Se 3 and BP. Bi 2 Se 3 flakes are synthesized by chemical vapor deposition 24 and transferred onto SiO 2 /Si substrate by polystyrene-assisted method 34 (details are found in Supporting Information Figure S2 and Section 4). Then, the mechanically exfoliated BP nanosheet is transferred to Bi 2 Se 3 via polydimethylsiloxane (PDMS) to form a p−n heterojunction (Figure S3 and Section 4).…”

“…This is because the carrier recombination in the device is mainly Shockley−Read−Hall (SRH) recombination in the junction region, 39 and the high-quality interface inhibits SRH recombination and promotes carrier transport. Next, we calculate the responsivity (R) and detectivity (D*) of the Bi 2 Se 3 /BP heterojunction photodetector according to the formulas R = I ph /(PS) and 34 where I ph represents photocurrent (I ph = I light − I dark ), P is the laser power density, S is the effective light sensitivity area of the device, and Δf and i n represent bandwidth and equivalent noise current, respectively. The noise power spectra of Bi 2 Se 3 /BP photodetector at 0 bias are shown in Figure S12, which is 2 orders of magnitude lower than the Bi 2 Se 3 photoconductive photodetector (Figure S1d).…”

Two-dimensional material assisted-growth strategy: new insights and opportunities

“…Oxygen's dual role in acting as an etching agent and inhibiting MoO 3 precursor source poisoning has been systematically verified, underscoring its paramount significance in the growth process. It is reported that Bi 2 Te 3 thin films with controllable thickness (one to several layers) were successfully synthesized by H 2 -assisted CVD [95]. The growth rate of H 2 is as high as 48 μm min −1 , which is 10 times faster than that of conventional methods, because it has strong reducibility and substrate passivation.…”