Confined van der Waals Epitaxial Growth of Two-Dimensional Large Single-Crystal In ₂ Se ₃ for Flexible Broadband Photodetectors

Abstract

<jats:p>The controllable growth of two-dimensional (2D) semiconductors with large domain sizes and high quality is much needed in order to reduce the detrimental effect of grain boundaries on device performance but has proven to be challenging. Here, we analyze the precursor concentration on the substrate surface which significantly influences nucleation density in a vapor deposition growth process and design a confined micro-reactor to grow 2D In<jats:sub>2</jats:sub>Se<jats:sub>3</jats:sub> with large domain sizes and high quality. The uniqueness of this confined micro-reactor is that its size is ~10<jats:sup>2</jats:sup>-10<jats:sup>3</jats:sup> times smaller than that of a conventional reactor. Such a remarkably small reactor causes a very low precursor concentration on the substrate surface, which reduces nucleation density and leads to the growth of 2D In<jats:sub>2</jats:sub>Se<jats:sub>3</jats:sub> grains with sizes larger than 200 <jats:italic>μ</jats:italic>m. Our experimental results show large domain sizes of the 2D In<jats:sub>2</jats:sub>Se<jats:sub>3</jats:sub> with high crystallinity. The flexible broadband photodetectors based on the as-grown In<jats:sub>2</jats:sub>Se<jats:sub>3</jats:sub> show rise and decay times of 140 ms and 25 ms, efficient response (5.6 A/W), excellent detectivity (7×10<jats:sup>10</jats:sup> Jones), high external quantum efficiency (251%), good flexibility, and high stability. This study, in principle, provides an effective strategy for the controllable growth of high quality 2D materials with few grain boundaries.</jats:p>

Localized Strain Measurement in Molecular Beam Epitaxially Grown Chalcogenide Thin Films by Micro-Raman Spectroscopy

“…This zero-strain phonon frequency ω 0In 2 Se 3 is consistent with the measured values reported by Zhou et al . (108.5 cm –1 ) and Tang et al (108 cm –1 ) for the transferred β-In 2 Se 3 film. The BiInSe 3 buffer layer is less than 10 nm, and the In 2 Se 3 layer thickness is more than 70 nm.…”

“…Assuming the strain in the exfoliated samples is relaxed (ω 0In 2 Se 3 = 108.11 cm −1 ), the phonon frequency shift (∼1.78 cm −1 ) is caused by strain in the MBE growth. This zero-strain phonon frequency ω 0In 2 Se 3 is consistent with the measured values reported by Zhou et al 24 (108.5 cm −1 ) and Tang et al 25 (108 cm −1 ) for the transferred β-In 2 Se 3 film. The BiInSe 3 buffer layer is less than 10 nm, and the In 2 Se 3 layer thickness is more than 70 nm.…”

Self-Powered Photoelectrochemical Photodetectors Based on Electrochemically Exfoliated In2Se3 Nanosheets

“…Figure S3b is the TEM image of 2D In 2 Se 3 nanosheets, further demonstrating that exfoliated 2D In 2 Se 3 nanosheets are thin. The lattice spacing is 0.348 nm as measured by the high-resolution TEM (HRTEM) image shown in Figure c, corresponding to the (100) lattice plane of In 2 Se 3 , consistent with previous reports Figure d shows XRD patterns of exfoliated and annealed 2D In 2 Se 3 nanosheets, which is consistent with α-In 2 Se 3 (PDF# 34-1279). , The (002) peak of exfoliated 2D In 2 Se 3 takes blue shifts, indicating that the crystal space increases due to the residual organic intercalator .…”

2D-Material-Based Volatile and Nonvolatile Memristive Devices for Neuromorphic Computing

“…These materials show stable switchable polarization and excellent optical properties. Thus, 2D ferroelectric materials can be applied in ferroelectric FETs (Fe-FETs) for nonvolatile memory and optoelectronic devices. − In a word, all these 2D materials have a wide range of application in FETs, , photodetectors, , and memristive devices ,, due to their characteristics of atomic-scale thickness, dangling-bond-free surface, and exceptional electronic and optoelectronic properties. They have attracted much attention in recent years.…”