Advanced Electronic Materials

Inorganic CsPbX₃ perovskites with compositions including CsPbBr_xCl_3−x, CsPbBr₃, and CsPbBr_xI_3−x are synthesized, and their properties are investigated. Tauc plots calculated from the UV–vis spectra of the materials show that the bandgaps of CsPbBr_xCl_3−x, CsPbBr₃, and CsPbBr_xI_3−x are 2.7, 2.35, and 1.8 eV, respectively. The as‐prepared CsPbX₃ nanodots have a cubic structure and their crystal sizes are around 5–10 nm. The diffraction peak intensity of the (110) plane is increased by adding Cl anion and reduced by adding I anion. By contrast, the peak intensity of the (200) plane is reduced by the introduction of Cl⁻ ions and increased by the introduction of I⁻ ions, suggesting that the nature of the halide anions affects the crystal orientation of CsPbX₃ quantum dots. The highest occupied molecular orbital/lowest unoccupied molecular orbital levels of CsPbBr_xCl_3−x, CsPbBr₃, and CsPbBr_xI_3−x calculated from ultraviolet photoemission spectra and UV–vis spectra are 6.5/3.8, 6.5/4.15, and 6.1/4.3 eV, respectively. The maximum luminance values measured for CsPbBr_xCl_3−x, CsPbBr₃, and CsPbBr_xI_3−x‐based light‐emitting diodes (LEDs) are 15.2, 51.7, and 21.7 cd m⁻², respectively. This research provides an overview of the energy levels and crystal structures of CsPbX₃ quantum dots for the design of inorganic perovskite‐based LEDs with high luminance and power efficiencies.

The hysteretic behavior of organic–inorganic halide perovskites (OHPs) are exploited for application in neuromorphic electronics. Artificial synapses with 2D and quasi‐2D perovskite are demonstrated that have a bulky organic cation (phenethylammonium (PEA)) to form structures of (PEA)₂MA_n‐1Pb_nBr_3n+1. The OHP films have morphological properties that depend on their structure dimensionality (i.e., n value), and artificial synapses fabricated from them show synaptic responses such as short‐term plasticity, paired‐pulse facilitation, and long‐term plasticity. The operation mechanism of OHP artificial synapses are also analyzed depending on the dimensionality and it is found that quasi‐2D (n = 3–5) OHP artificial synapses show much longer retention than 2D and 3D OHP counterparts. The calculated energy consumption of a 2D OHP artificial synapse (≈0.7 fJ per synaptic event) is comparable to that of biological synapses (1–10 fJ per synaptic event). These OHP artificial synapses may enable development of neuromorphic electronics that use very little energy.

2D materials are considered promising candidates for developing next‐generation high‐performance energy efficient electronic, optoelectronic, and valley‐tronic devices. Though metal oxides are widely used in the fabrication of many advanced devices, very little work has been reported on their properties in 2D limit. This article reports the discovery of a new 2D materials system, 2D tin monoxide (SnO). Layer by layer growth of SnO on sapphire and SiO₂ substrates is demonstrated using a pulsed laser deposition method. The number of SnO layers is controlled by controlling the number of laser shots during the deposition process. Raman spectroscopic and X‐ray photoelectron spectroscopic analysis confirms the formation of phase pure SnO layers. Field effect transistors (FETs) using few layer SnO channels grown on SiO₂ substrates are successfully fabricated. These FETs show typical p‐channel conduction with field effect mobility ranging from 0.05 to 1.9 cm² V⁻¹ s⁻¹. Field effect mobility varies with the number of SnO layers and decreases on either sides of the optimum layer numbers (12), which is explained based on charge screening and interlayer coupling in layered materials.

A method to modulate the threshold voltage of a graphene–ZnO barristor is investigated. Two types of polymers, polyethyleneimine (as an n‐type dopant) and poly (acrylic acid) (as a p‐type dopant), are used to pre‐set the initial Fermi level of the graphene. The threshold voltage of the graphene barristor can be modulated between −2.0 V (n‐type graphene) and 1.2 V (p‐type graphene) while modulating the Fermi level of the graphene by 120 meV. This process provides a scalable and facile method to adjust the threshold voltage of graphene–semiconductor junction‐based devices, which is a crucial function required to implement graphene‐based electronic devices in integrated circuits.

Emerging van der Waals heterojunctions (vdWH) containing 2D materials have shown exciting functionalities that surpass those of traditional devices based on bulk materials. In this Communication, a report on the properties of a 2D sulfide/oxide hybrid vdWH based on n‐type molybdenum disulfide (MoS₂) and p‐type tin monoxide (SnO) is presented, with promising rectification, thermal‐sensing, and photosensing performance. Specifically, the hybrid SnO/MoS₂ vdWH shows static rectification ratio of 2 × 10² with ideality factor of 2.3, and can operate at 100 Hz with good stability. The vdWH shows good temperature stability with reversible and reproducible current levels up to 110 °C, indicating its potential for thermal sensing applications. The sensitivity of current variation is calculated to be 0.0144 dec °C⁻¹. Finally, maximum responsivity of 8.17 mA W⁻¹ and external quantum efficiency of 2.14% have been achieved in photovoltaic measurements. The results suggest that MoS₂–SnO hybrid vdWH are promising for various sensing applications.

This study reports on a reconfigurable antenna platform based on vanadium dioxide (VO₂), a phase‐change material (PCM) with low transition temperature, integrated with an addressable microheater matrix. For the first time, it is shown that an entire planar antenna can be thermally reconfigured virtually to any pattern by switching the phase of the selected regions of the VO₂ layer from insulator to metallic state by indirect thermal stimuli generated by individually addressable nichrome resistive microheaters. Careful selection of the individual pixels to start the phase transition from insulator (OFF) to metallic (ON) state allows creating different antenna patterns with unique resonance properties. Reconfiguring the antenna into different patterns, operating frequency can be tuned from C‐band (4–8 GHz) to X‐band (8–12 GHz), and S‐band (2–4 GHz) frequencies which cover the entire ultra wideband spectrum (3.1–10.6 GHz). The proposed approach provides a promising platform for designing monolithically integrated reconfigurable antennas, radio frequency devices, and circuits for various applications.

An amorphous indium gallium zinc oxide (a‐IGZO) layer is deposited on very thin conductive amorphous indium zinc oxide (a‐IZO) thin film to demonstrate high‐performance, coplanar thin‐film transistors (TFTs) with dual‐channel oxide semiconductor architecture. Based on material properties, a conduction band offset (∆E_C) of ≈0.28 eV between a‐IZO and a‐IGZO layers and a conduction band bending of ≈0.3 eV at a‐IGZO/gate insulator (GI) interface exist. Through the electrical characterization, high field‐effect mobility (μ_FE) of ≈50 cm² V⁻¹ s⁻¹, a positive threshold voltage (V_Th) of ≈2.3 V, and low off‐current (I_OFF) of <1 pA in coplanar a‐IZO/a‐IGZO TFT are demonstrated. The electron accumulation (>5 × 10¹⁸ cm⁻³) at both the a‐IZO/a‐IGZO and a‐IGZO/GI interfaces confirm the dual‐channel conduction. The bottom a‐IZO channel significantly contributes to increasing drain current (I_D) due to large electron density (≈10¹⁹ cm⁻³). The dual‐channel coplanar TFT with a‐IGZO/IZO provides a guideline for overcoming the trade‐off between high μ_FE and positive V_Th control for stable enhancement mode operation with increased I_D.

The dependence of charge carrier mobility on semiconductor channel thickness in field‐effect transistors is a universal phenomenon that has been studied extensively for various families of materials. Surprisingly, analogous studies involving metal oxide semiconductors are relatively scarce. Here, spray‐deposited In₂O₃ layers are employed as the model semiconductor system to study the impact of layer thickness on quantum confinement and electron transport along the transistor channel. The results reveal an exponential increase of the in‐plane electron mobility (µ_e) with increasing In₂O₃ thickness up to ≈10 nm, beyond which it plateaus at a maximum value of ≈35 cm² V⁻¹ s⁻¹. Optical spectroscopy measurements performed on In₂O₃ layers reveal the emergence of quantum confinement for thickness <10 nm, which coincides with the thickness that µ_e starts deteriorating. By combining two‐ and four‐probe field‐effect mobility measurements with high‐resolution atomic force microscopy, it is shown that the reduction in µ_e is attributed primarily to surface scattering. The study provides important guidelines for the design of next generation metal oxide thin‐film transistors.

An cross‐bar structure is employed to design a transparent p‐n junction‐based photodetector. The device consisting of aligned n‐SnO₂ and p‐NiO nanofibers is prepared via a mature electrospinning process that is suitable for commercial applications. It exhibits a high detectivity of 2.33 × 10¹³ Jones under 250 nm illumination at −5 V, outperforming most state‐of‐art SnO₂‐based UV photodetectors. It is also endowed with a self‐powered feature due to a photovoltaic effect from the p‐n junction, resulting in a photocurrent of 10⁻¹⁰ A, responsivity of 30.29 mA W⁻¹ at 0 V bias, and detectivity of 2.24 × 10¹¹ Jones at 0.05 V bias. Moreover, the device is highly transparent (over 90% toward visible light) due to the wide band gap of photoactive materials and well‐designed cross‐bar fiber structure. Additionally, an n‐SnO₂‐p‐ZnO:Ag (Ag doped ZnO) self‐powered UV photodetector is fabricated that shows good performance and give another example of the use of the cross‐bar structure.

Sự phát triển nhanh chóng của các công nghệ hữu cơ mới đã dẫn đến những ứng dụng quan trọng của thiết bị điện tử hữu cơ như đi-ốt phát sáng, pin năng lượng mặt trời và bóng bán dẫn hiệu ứng trường. Yêu cầu lớn hiện nay là chất dẫn điện có độ dẫn cao và tính trong suốt để có thể hoạt động như lớp chuyển tải điện tích hoặc kết nối điện trong các thiết bị hữu cơ. Poly(3,4-ethylenedioxythiophene): poly(styrenesulfonic acid) (PEDOT:PSS), được biết đến như là chất dẫn điện nổi bật nhất, đã đảm nhận vai trò này nhờ vào khả năng tạo màng tốt, tính trong suốt cao, độ dẫn điện điều chỉnh được và độ ổn định nhiệt tuyệt vời. Bài tổng quan này tóm tắt các phương pháp hóa học và vật lý thú vị có thể nâng cao hiệu quả độ dẫn điện của PEDOT:PSS một cách hiệu quả, đặc biệt tập trung vào cơ chế nâng cao độ dẫn cũng như ứng dụng của các màng PEDOT:PSS. Những triển vọng cho các nỗ lực nghiên cứu trong tương lai cũng được đề cập. Dự kiến rằng các màng PEDOT:PSS với độ dẫn cao và tính trong suốt có thể là trọng điểm cho những đột phá vật liệu điện tử hữu cơ trong tương lai.