Wafer-Scale Atomic Layer-Deposited TeO/Te Heterostructure P-Type Thin-Film Transistors.

There is an increasing demand for p-type semiconductors with scalable growth, excellent device performance, and back-end-of-line (BEOL) compatibility. Recently, tellurium (Te) has emerged as a promising candidate due to its appealing electrical properties and potential low-temperature production. So far, nearly all of the scalable production and integration of Te with complementary metal oxide semiconductor (CMOS) technology have been based on physical vapor deposition.

Hydrogen-induced tunable remanent polarization in a perovskite nickelate.

Materials with field-tunable polarization are of broad interest to condensed matter sciences and solid-state device technologies. Here, using hydrogen (H) donor doping, we modify the room temperature metallic phase of a perovskite nickelate NdNiO into an insulating phase with both metastable dipolar polarization and space-charge polarization. We then demonstrate transient negative differential capacitance in thin film capacitors.

Superconducting Field-Effect Transistors with PdTe-Te Intimate Contacts.

Superconducting-based electronic devices have shown great potential for future quantum computing applications. One key building block device is a superconducting field-effect transistor based on a superconductor-semiconductor-superconductor Josephson-junction (JJ) with a gate-tunable semiconducting channel. However, the performance of such devices is highly dependent on the quality of the superconductor to semiconductor interface.

Optically Gated Electrostatic Field-Effect Thermal Transistor.

Dynamic tuning of thermal transport in solids is scientifically intriguing with wide applications for thermal transport control in electronic devices. In this work, we demonstrate a thermal transistor, a device in which heat flow can be regulated using external control, realized in a topological insulator (TI) through the topological surface states. The tuning of thermal transport is achieved by using optical gating of a thin dielectric layer deposited on the TI film.

Review-Extremely Thin Amorphous Indium Oxide Transistors.

Amorphous oxide semiconductor transistors have been a mature technology in display panels for upward of a decade, and have recently been considered as promising back-end-of-line compatible channel materials for monolithic 3D applications. However, achieving high-mobility amorphous semiconductor materials with comparable performance to traditional crystalline semiconductors has been a long-standing problem. Recently it has been found that greatly reducing the thickness of indium oxide, enabled by an atomic layer deposition (ALD) process, can tune its material properties to achieve high mobility, high drive current, high on/off ratio, and enhancement-mode operation at the same time, beyond the capabilities of conventional oxide semiconductor materials.

Self-Assembled Au Nanoelectrodes: Enabling Low-Threshold-Voltage HfO-Based Artificial Neurons.

Filamentary-type resistive switching devices, such as conductive bridge random-access memory and valence change memory, have diverse applications in memory and neuromorphic computing. However, the randomness in filament formation poses challenges to device reliability and uniformity. To overcome this issue, various defect engineering methods have been explored, including doping, metal nanoparticle embedding, and extended defect utilization.

Tunable Chirality-Dependent Nonlinear Electrical Responses in 2D Tellurium.

Tellurium (Te) is an elemental semiconductor with a simple chiral crystal structure. Te in a two-dimensional (2D) form synthesized by a solution-based method shows excellent electrical, optical, and thermal properties. In this work, the chirality of hydrothermally grown 2D Te is identified and analyzed by hot sulfuric acid etching and high-angle tilted high-resolution scanning transmission electron microscopy.

Tunable Circular Photogalvanic and Photovoltaic Effect in 2D Tellurium with Different Chirality.

Chirality arises from the asymmetry of materials, where two counterparts are the mirror image of each other. The interaction between circular-polarized light and quantum materials is enhanced in chiral space groups due to the structural chirality. Tellurium (Te) possesses the simplest chiral crystal structure, with Te atoms covalently bonded into a spiral atomic chain (left- or right-handed) with a periodicity of 3.

ZnO-ferromagnetic metal vertically aligned nanocomposite thin films for magnetic, optical and acoustic metamaterials.

Magnetoacoustic waves generated in piezoelectric and ferromagnetic coupled nanocomposite films through magnetically driven surface acoustic waves present great promise of loss-less data transmission. In this work, ferromagnetic metals of Ni, Co and Co Ni are coupled with a piezoelectric ZnO matrix in a vertically-aligned nanocomposite (VAN) thin film platform. Oxidation was found to occur in the cases of ZnO-Co, forming a ZnO-CoO VAN, while only very minor oxidation was found in the case of ZnO-Ni VAN.

Nanometer-Thick Oxide Semiconductor Transistor with Ultra-High Drain Current.

High drive current is a critical performance parameter in semiconductor devices for high-speed, low-power logic applications or high-efficiency, high-power, high-speed radio frequency (RF) analogue applications. In this work, we demonstrate an InO transistor grown by atomic layer deposition (ALD) at back-end-of-line (BEOL) compatible temperatures with a record high drain current in planar FET, exceeding 10 A/mm, the performance of which is 2-3 times better than all known transistors with semiconductor channels. A high transconductance reaches 4 S/mm, recorded among all transistors with a planar structure.

Ionic Control over Ferroelectricity in 2D Layered van der Waals Capacitors.

The van der Waals layered material CuInPS features interesting functional behavior, including the existence of four uniaxial polarization states, polarization reversal against the electric field through Cu ion migration, a negative-capacitance regime, and reversible extraction of Cu ions. At the heart of these characteristics lies the high mobility of Cu ions, which also determines the spontaneous polarization. Therefore, Cu migration across the lattice results in unusual ferroelectric behavior.

First demonstration of robust tri-gate-GaOnano-membrane field-effect transistors.

Nano-membrane tri-gate-gallium oxide (-GaO) field-effect transistors (FETs) on SiO/Si substrate fabricated via exfoliation have been demonstrated for the first time. By employing electron beam lithography, the minimum-sized features can be defined with the footprint channel width of 50 nm. For high-quality interface between-GaOand gate dielectric, atomic layer-deposited 15 nm thick aluminum oxide (AlO) was utilized with tri-methyl-aluminum (TMA) self-cleaning surface treatment.

Mechanical Anisotropy in Two-Dimensional Selenium Atomic Layers.

Two-dimensional (2D) trigonal selenium (-Se) has become a new member in 2D semiconducting nanomaterial families. It is composed of well-aligned one-dimensional Se atomic chains bonded via van der Waals (vdW) interaction. The contribution of this unique anisotropic nanostructure to its mechanical properties has not been explored.

Bilayer Quantum Hall States in an n-Type Wide Tellurium Quantum Well.

Tellurium (Te) is a narrow bandgap semiconductor with a unique chiral crystal structure. The topological nature of electrons in the Te conduction band can be studied by realizing n-type doping using atomic layer deposition (ALD) technique on two-dimensional (2D) Te film. In this work, we fabricated and measured the double-gated n-type Te Hall-bar devices, which can operate as two separate or coupled electron layers controlled by the top gate and back gate.

Asymmetric Metal/α-InSe/Si Crossbar Ferroelectric Semiconductor Junction.

A ferroelectric semiconductor junction is a promising two-terminal ferroelectric device for nonvolatile memory and neuromorphic computing applications. In this work, we propose and report the experimental demonstration of asymmetric metal/α-InSe/Si crossbar ferroelectric semiconductor junctions (c-FSJs). The depletion in doped Si is used to enhance the modulation of the effective Schottky barrier height through the ferroelectric polarization.

Why InO Can Make 0.7 nm Atomic Layer Thin Transistors.

In this work, we demonstrate enhancement-mode field-effect transistors by an atomic-layer-deposited (ALD) amorphous InO channel with thickness down to 0.7 nm. Thickness is found to be critical on the materials and electron transport of InO.

Indium-Tin-Oxide Transistors with One Nanometer Thick Channel and Ferroelectric Gating.

In this work, we demonstrate high-performance indium-tin-oxide (ITO) transistors with a channel thickness down to 1 nm and ferroelectric HfZrO as gate dielectric. An on-current of 0.243 A/mm is achieved on submicron gate-length ITO transistors with a channel thickness of 1 nm, while it increases to as high as 1.

Anisotropic Signal Processing with Trigonal Selenium Nanosheet Synaptic Transistors.

Hardware implementation of an artificial neural network requires neuromorphic devices to process information with low energy consumption and high heterogeneity. Here we demonstrate an electrolyte-gated synaptic transistor (EGT) based on a trigonal selenium (-Se) nanosheet. Due to the intrinsic low conductivity of the Se channel, the -Se synaptic transistor exhibits ultralow energy consumption, less than 0.

Ultrafast photoinduced band splitting and carrier dynamics in chiral tellurium nanosheets.

Trigonal tellurium (Te) is a chiral semiconductor that lacks both mirror and inversion symmetries, resulting in complex band structures with Weyl crossings and unique spin textures. Detailed time-resolved polarized reflectance spectroscopy is used to investigate its band structure and carrier dynamics. The polarized transient spectra reveal optical transitions between the uppermost spin-split H and H and the degenerate H valence bands (VB) and the lowest degenerate H conduction band (CB) as well as a higher energy transition at the L-point.

Quantum Hall effect of Weyl fermions in n-type semiconducting tellurene.

Dirac and Weyl nodal materials can host low-energy relativistic quasiparticles. Under strong magnetic fields, the topological properties of Dirac/Weyl materials can directly be observed through quantum Hall states. However, most Dirac/Weyl nodes generically exist in semimetals without exploitable band gaps due to their accidental band-crossing origin.

Solar-Blind UV Photodetector Based on Atomic Layer-Deposited CuO and Nanomembrane β-GaO pn Oxide Heterojunction.

Herein, we present a solar-blind ultraviolet photodetector realized using atomic layer-deposited p-type cuprous oxide (CuO) underneath a mechanically exfoliated n-type β-gallium oxide (β-GaO) nanomembrane. The atomic layer deposition process of the CuO film applies bis(,'-di-secbutylacetamidinato)dicopper(I) [Cu(Bu-Me-amd)] as a novel Cu precursor and water vapor as an oxidant. The exfoliated β-GaO nanomembrane was transferred to the top of the CuO layer surface to realize a unique oxide pn heterojunction, which is not easy to realize by conventional oxide epitaxy techniques.

Room-Temperature Electrocaloric Effect in Layered Ferroelectric CuInPS for Solid-State Refrigeration.

A material with reversible temperature change capability under an external electric field, known as the electrocaloric effect (ECE), has long been considered as a promising solid-state cooling solution. However, electrocaloric (EC) performance of EC materials generally is not sufficiently high for real cooling applications. As a result, exploring EC materials with high performance is of great interest and importance.

Thermoelectric Performance of 2D Tellurium with Accumulation Contacts.

Tellurium (Te) is an intrinsically p-type-doped narrow-band gap semiconductor with an excellent electrical conductivity and low thermal conductivity. Bulk trigonal Te has been theoretically predicted and experimentally demonstrated to be an outstanding thermoelectric material with a high value of thermoelectric figure-of-merit ZT. In view of the recent progress in developing the synthesis route of 2D tellurium thin films as well as the growing trend of exploiting nanostructures as thermoelectric devices, here for the first time, we report the excellent thermoelectric performance of tellurium nanofilms, with a room-temperature power factor of 31.

Imaging Carrier Inhomogeneities in Ambipolar Tellurene Field Effect Transistors.

The development of van der Waals (vdW) homojunction devices requires materials with narrow bandgaps and simultaneously high hole and electron mobilities for bipolar transport, as well as methods to image and study spatial variations in carrier type and associated conductivity with nanometer spatial resolution. Here, we demonstrate the general capability of near-field scanning microwave microscopy (SMM) to image and study the local carrier type and associated conductivity in operando by studying ambiploar field-effect transistors (FETs) of the 1D vdW material tellurium in 2D form. To quantitatively understand electronic variations across the device, we produce nanometer-resolved maps of the local carrier equivalence backgate voltage.

Ultrafast measurements of polarization switching dynamics on ferroelectric and anti-ferroelectric hafnium zirconium oxide.

The ultrafast measurements of polarization switching dynamics on ferroelectric (FE) and antiferroelectric (AFE) hafnium zirconium oxide (HZO) are studied. The transient current during the polarization switching process is probed directly on the nanosecond scale. The switching time is determined to be as fast as 10 ns to reach fully switched polarization with characteristic switching times of 5.