Jiuxiang Dai

Room-temperature ferromagnetism was achieved for a Cu intercalated, amorphous 2D Cu/WO₃. Experimental and theoretical investigations suggest the magnetic enhancement of 2D Cu/WO₃ is originated from oxygen lattice distortion induced by Cu intercalation, leading to the formation of bound magnetic polaron for ferromagnetism.

Abstract

Ferromagnetism in the two-dimensional limit has become an intriguing topic for exploring new physical phenomena and potential applications. To induce ferromagnetism in 2D materials, intercalation has been proposed to be an effective strategy, which could introduce lattice distortion and unpaired spin into the material to modulate the magnetocrystalline anisotropy and magnetic exchange interactions. To strengthen the understanding of the magnetic origin of 2D material, Cu was introduced into a 2D WO₃ through chemical intercalation in this work (2D Cu/WO₃). In contrast to the diamagnetic nature of Cu and WO₃, room-temperature ferromagnetism was characterized for 2D Cu/WO₃. Experimental and theoretical results attribute the ferromagnetism to the bound magnetic polaron in 2D Cu/WO₃, which is consist of unpaired spins from W⁵⁺/W⁴⁺ with localized carriers from oxygen vacancies. Overall, this work provides a novel approach to introduce ferromagnetism into diamagnetic WO₃, which could be applied for a wider scope of 2D materials.

While complex oxide heterostructures can exhibit a wide range of remarkable phenomena, the properties can depend strongly on size. Results from in situ synchrotron X-ray studies demonstrate the close interactions between structure, stoichiometry, and magnetism in the ultrathin LaCoO₃ epitaxial films, revealing novel methods for the manipulation of material properties at the unit cell level.

Abstract

It is well known that the properties of a crystal evolve as it increases in size from a single atomic plane to that of the bulk. Such size-dependent transitions can stem from many different origins and depend on minute changes to crystal bonding and composition. A model example is that of LaCoO₃, which is non-magnetic in the bulk but can display ferromagnetism at the nanoscale. Here, the evolution of structure-property relationships is studied in the LaCoO_3−δ/SrTiO₃ (001) system as the thickness of LaCoO_3−δ is increased from a single plane to 10 unit cells. In situ synchrotron X-ray studies are performed during and post-deposition to probe changes in the interactions between structure, stoichiometry, and magnetic behavior. Structural quantification indicates that the oxygen octahedral rotation pattern evolves with thickness, due to inherent differences in crystal symmetry between the film and substrate. The change in rotation modifies the required energy barrier for the spin state transition via the Co–O bond length and Co–O–Co bond angle, affecting the appearance of ferromagnetism. Our results highlight the contributions of high spin Co²⁺ and/or high spin Co³⁺ to respective weak and robust ferromagnetism and the evolution of properties with size in ultrathin LaCoO_3−δ heterostructures.

Mutual atomic to micrometer scale hierarchical structural integration of Cu₂Se and CuGaSe₂ phases enables strong entanglement of their electronic structure leading to hybridization of their native electronic defects for nearly equimolar composites.

Abstract

Engineering the energy distribution of electronic defects in semiconductors can afford the coexistence of degenerate and nondegenerate transport behavior. By leveraging native defects in Cu₂Se and CuGaSe₂ phases, the tunability of the concentration and energy distribution of active electronic defects in hierarchical (1-x)Cu₂Se-(x)CuGaSe₂ composites is demonstrated. This study found that the electrical conductivity of various composites decreases with rising temperature indicating degenerate semiconducting behavior, whereas the carrier density increases with temperature, which is consistent with non-degenerate semiconductivity. Remarkably, this study found that while the carrier density and electrical conductivity drop with the increasing CuGaSe₂ content for samples with x ≤ 0.45 is consistent with an increase in the activation energy of “active” electronic defects, the sudden increase by 140% in the electrical conductivity and by 109% in the carrier density for near equimolar composition suggests the formation of a large density of electronic defects with lower activation energy. This unusual behavior is understood within the context of the hybridization of coexisting native electronic defects to form degenerate hybrid acceptor states with lower activation energy. The reported unique electronic transport can be leveraged for the development of more versatile electronic and optoelectronic devices with superior performance.

Presenting a novel approach, this study demonstrates sustained area-selectivity in atomic layer deposition (ALD) of Ir films. Leveraging the dual effects of O₃, it achieves area-selective deposition on Al₂O₃ surfaces while etching Ir nuclei on SiO₂ surfaces. Through precise control of O₃ injection, sustained area-selectivity is achieved, promising advancements in thin-film technologies.

Abstract

Area-selective deposition (ASD) based on self-aligned technology has emerged as a promising solution for resolving misalignment issues during ultrafine patterning processes. Despite its potential, the problems of area-selectivity losing beyond a certain thickness remain critical in ASD applications. This study reports a novel approach to sustain the area-selectivity of Ir films as the thickness increases. Ir films are deposited on Al₂O₃ as the growth area and SiO₂ as the non-growth area using atomic-layer-deposition with tricarbonyl-(1,2,3-η)-1,2,3-tri(tert-butyl)-cyclopropenyl-iridium and O₃. O₃ exhibits a dual effect, facilitating both deposition and etching. In the steady-state growth regime, O₃ solely contributes to deposition, whereas in the initial growth stages, longer exposure to O₃ etches the initially formed isolated Ir nuclei through the formation of volatile IrO₃. Importantly, longer O₃ exposure is required for the initial etching on the growth area(Al₂O₃) compared to the non-growth area(SiO₂). By controlling the O₃ injection time, the area selectivity is sustained even above a thickness of 25 nm by suppressing nucleation on the non-growth area. These findings shed light on the fundamental mechanisms of ASD using O₃ and offer a promising avenue for advancing thin-film technologies. Furthermore, this approach holds promise for extending ASD to other metals susceptible to forming volatile species.

Diversified thermodynamically advantageous slip stackings with angstrom-scale structural discrepancies are constructed in low-symmetry van der Waals homobilayers via direct growth. Modulation strategies to switch the stacking via grain boundaries and to expand the slip stacking library from thermodynamic to kinetically favored structures via in situ thermal treatment are developed. The work unveils a unique epitaxy and offers a viable means for manipulating interlayer atomic registries.

Abstract

The van der Waals (vdW) interface provides two important degrees of freedom—twist and slip—to tune interlayer structures and inspire unique physics. However, constructing diversified high-quality slip stackings (i.e., lattice orientations between layers are parallel with only interlayer sliding) is more challenging than twisted stackings due to angstrom-scale structural discrepancies between different slip stackings, sparsity of thermodynamically stable candidates and insufficient mechanism understanding. Here, using transition metal dichalcogenide (TMD) homobilayers as a model system, this work theoretically elucidates that vdW materials with low lattice symmetry and weak interlayer coupling allow the creation of multifarious thermodynamically advantageous slip stackings, and experimentally achieves 13 and 9 slip stackings in 1T″-ReS₂ and 1T″-ReSe₂ bilayers via direct growth, which are systematically revealed by atomic-resolution scanning transmission electron microscopy (STEM), angle-resolved polarization Raman spectroscopy, and second harmonic generation (SHG) measurements. This work also develops modulation strategies to switch the stacking via grain boundaries (GBs) and to expand the slip stacking library from thermodynamic to kinetically favored structures via in situ thermal treatment. Finally, density functional theory (DFT) calculations suggest a prominent dependence of the pressure-induced electronic band structure transition on stacking configurations. These studies unveil a unique vdW epitaxy and offer a viable means for manipulating interlayer atomic registries.

This work demonstrates that achieving an unnaturally high refractive index at optical frequencies is possible through colloidal self-assembly. By utilizing polymeric brush-assisted balancing between attractive and repulsive potentials, polyhedral gold nanoparticles (i.e., nanocubes) are self-assembled into a close-packed monolayer with high macroscopic integrity and crystallinity. This represents the first realization of an optical metasurface with a refractive index of 10-plus, which is out of reach thus far.

Abstract

This study demonstrates the developments of self-assembled optical metasurfaces to overcome inherent limitations in polarization density (P) and high refractive indices (n) within naturally occurring materials. The Maxwellian macroscopic description establishes a link between P and n, revealing a static limit in natural materials, restricting n to ≈4.0 at optical frequencies. Previously, it is accepted that self-assembly enables the creation of nanogaps between metallic nanoparticles (NPs), boosting capacitive enhancement of P and resultant exceptionally high n at optical frequencies. The work focuses on assembling gold (Au) NPs into a closely packed monolayer by rationally designing the polymeric ligand to balance attractive and repulsive forces, in that polymeric brush-mediated self-assembly of the close-packed Au NP monolayer is robustly achieved over a large-area. The resulting monolayer of Au nanospheres (NSs), nanooctahedras (NOs), and nanocubes (NCs) exhibits high macroscopic integrity and crystallinity, sufficiently enough for pushing n to record-high regimes. The systematic comparisons between each differently shaped Au NP monolayers elucidate the significance of capacitive coupling in achieving an unnaturally high n. The achieved n of 10.12 at optical frequencies stands as a benchmark, highlighting the potential of polyhedral Au NPs in advancing optical metasurfaces.

Compared to commercial noble-metal-based platinum/carbon electrocatalysts, an emerging organic/inorganic heterojunction material system is presented that demonstrates outstanding enhancements in electrochemical catalytic capability and structural stability due to the formation of P-N heterojunction interfaces between N-type exfoliated MoS₂ nanosheets and P-type polyaniline. This system exhibits promising performance and stable operation in fuel cell devices, confirming its potential for application in various catalytic and energy fields.

Abstract

We have achieved a significant breakthrough in the preparation and development of two-dimensional nanocomposites with P-N heterojunction interfaces as efficient cathode catalysts for electrochemical hydrogen evolution reaction (HER) and iodide oxidation reaction (IOR). P-type acid-doped polyaniline (PANI) and N-type exfoliated molybdenum disulfide (MoS₂) nanosheets can form structurally stable composites due to formation of P-N heterojunction structures at their interfaces. These P-N heterojunctions facilitate charge transfer from PANI to MoS₂ structures and thus significantly enhance the catalytic efficiency of MoS₂ in the HER and IOR. Herein, by combining efficient sodium-functionalized chitosan-assisted MoS₂ exfoliation, electropolymerization of PANI on nickel foam (NF) substrate, and electrochemical activation, controllable and scalable Na-Chitosan/MoS₂/PANI/NF electrodes are successfully constructed as non-noble metal-based electrochemical catalysts. Compared to a commercial platinum/carbon (Pt/C) catalyst, the Na-Chitosan/MoS₂/PANI/NF electrode exhibits significantly lower resistance and overpotential, a similar Tafel slope, and excellent catalytic stability at high current densities, demonstrating excellent catalytic performance in the HER under acidic conditions. More importantly, results obtained from proton exchange membrane fuel cell devices confirm the Na-Chitosan/MoS₂/PANI/NF electrode exhibits a low turn-on voltage, high current density, and stable operation at 2 V. Thus, this system holds potential as a replacement for Pt/C with feasibility for applications in energy-related fields.

Abstract

Two-dimensional (2D) semiconductors with intrinsic ferromagnetism are highly desirable for potential applications in nextgeneration spintronic and optoelectronic devices. However, controllable synthesis of intrinsic 2D magnetic semiconductor on a substrate is still a challenging task. Herein, large-area 2D non-layered rock salt (α-phase) MnSe nanosheets were grown on mica substrates, with the thickness changing from 54.2 to 0.9 nm (one unit cell), by chemical vapour deposition. The X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy measurements confirmed that the resulting 2D α-MnSe nanosheets were obtained as high-quality single crystals. The magnetic hysteresis loops and synchrotron X-ray measurements directly indicated the anomalous magnetic properties in α-MnSe nanosheets. Comprehensive analysis of the reasons for magnetic property revealed that the low-temperature phase transition, small number of stacking differences in crystals, and surface weak oxidation in (111)-oriented α-MnSe were the main mechanisms. Furthermore, α-MnSe nanosheets exhibited broadband photoresponse from 457 to 671 nm with an outstanding detectivity and responsivity behaviours. This study presents the detailed growth process of ultrathin 2D magnetic semiconductor α-MnSe, and its outstanding magnetic properties and broadband photodetection, which provide an excellent platform for magneto–optical and magneto–optoelectronic research.

Nature Electronics, Published online: 29 July 2024; doi:10.1038/s41928-024-01210-3

This Perspective explores key challenges in the development of electronics based on two-dimensional transition metal dichalcogenides, identifying defects, doping, p-type contacts and high-dielectric-constant dielectrics as critical issues.

Abstract

Van der Waals (vdWs) stacking of two-dimensional (2D) materials can effectively weaken the Fermi level pinning (FLP) effect in metal/semiconductor contacts due to dangling-bond-free surfaces. However, the inherent vdWs gap always induces a considerable tunneling barrier, significantly limiting carrier injection. Herein, by inducing a sp² to sp³ hybridization transformation in 2D carbon-based metal via surface defect engineering, the large orbital overlap can form an efficient carrier channel, overcoming the tunneling barrier. Specifically, by selecting the 2D carbon-based X₃C₂ (X = Cd, Hg, and Zn) metal and the 2D MSi₂N₄ (M = Cr, Hf, Mo, Ti, V, and Zr) semiconductor, we constructed 36 metal/semiconductor contacts. For vdWs contacts, although Ohmic contacts can be formed at the interface, the highest tunneling probability (P_TB) is only 3.11%. As expected, the P_TB can be significantly improved, as high as 48.73%, when MSi₂N₄, accompanied by surface nitrogen vacancies, forms an interface covalent bond with X₃C₂. Simultaneously, weak FLP and Ohmic contact remain at the covalent-bond-based surface, attributing to the protection of the MSi₂N₄ band-edge electronic states by the outlying Si-N sublayer. Our work provides a promising path for advancing the progress of 2D electronic and photoelectronic devices.

Nature Materials, Published online: 01 August 2024; doi:10.1038/s41563-024-01930-z

Real-time atomic-scale imaging reveals the presence of reversible transitions between ferroelectric and non-ferroelectric phases during electric stimuli, enabling the possibility for reliability improvement in ferroelectric materials compatible with complementary metal–oxide–semiconductors.

This study explores the synthesis of Tellurium sulfur oxide (TeSO_x) and Tellurium selenium oxide (TeSeO_x) nanomaterials via vapor deposition, highlighting their unique photo-synaptic responses to different optical stimulations. Further, TeSeO_x multiropes demonstrate their potential in optical neuromorphic computing through enhanced electrical performance and high responsivity achieved with low voltage and light intensity.

Abstract

Nanomaterials like graphene and transition metal dichalcogenides are being explored for developing artificial photosensory synapses with low-power optical plasticity and high retention time for practical nervous system implementation. However, few studies are conducted on Tellurium (Te)-based nanomaterials due to their direct and small bandgaps. This paper reports the superior photo-synaptic properties of covalently bonded Tellurium sulfur oxide (TeSO_x) and Tellurium selenium oxide (TeSeO_x)nanomaterials, which are fabricated by incorporating S and Se atoms on the surface of Te multiropes using vapor deposition. Unlike pure Te multiropes, the TeSO_x and TeSeO_x multiropes exhibit controllable temporal dynamics under optical stimulation. For example, the TeSO_x multirope-based transistor displays a photosensory synaptic response to UV light (λ = 365 nm). Furthermore, the TeSeO_x multirope-based transistor exhibits photosensory synaptic responses to UV–vis light (λ = 365, 565, and 660 nm), reliable electrical performance, and a combination of both photodetector and optical artificial synaptic properties with a maximum responsivity of 1500 AW⁻¹ to 365 nm UV light. This result is among the highest reported for Te-heterostructure-based devices, enabling optical artificial synaptic applications with low voltage spikes (1 V) and low light intensity (21 µW cm⁻²), potentially useful for optical neuromorphic computing.

This study visualizes light-induced ferroelectric polarization in an α-In₂Se₃/Te heterojunction using photocurrent mapping. The device shows nonvolatile photoresponsivity with photocurrent enhancement up to 1000 times after polarization saturation. These findings demonstrate the potential of 2D ferroelectric materials for advanced photodetectors and optical information storage applications.

Abstract

Light-induced ferroelectric polarization in 2D layered ferroelectric materials holds promise in photodetectors with multilevel current and reconfigurable capabilities. However, translating this potential into practical applications for high-density optoelectronic information storage remains challenging. In this work, an α-In₂Se₃/Te heterojunction design that demonstrates spatially resolved, multilevel, nonvolatile photoresponsivity is presented. Using photocurrent mapping, the spatially localized light-induced poling state (LIPS) is visualized in the junction region. This localized ferroelectric polarization induced by illumination enables the heterojunction to exhibit enhanced photoresponsivity. Unlike previous reports that observe multilevel polarization enhancement in electrical resistance, the device shows nonvolatile photoresponsivity enhancement under illumination. After polarization saturation, the photocurrent increases up to 1000 times, from 10⁻¹² to 10⁻⁹ A under the irradiation of a 520 nm laser with a power of 1.69 nW, compared to the initial state in a self-driven mode. The photodetector exhibits high detectivity of 4.6×10¹⁰ Jones, with a rise time of 27 µs and a fall time of 28 µs. Furthermore, the device's localized poling characteristics and multilevel photoresponse enable spatially multiplexed optical information storage. These results advance the understanding of LIPS in 2D ferroelectric materials, paving the way for optoelectronic information storage technologies.

Halide perovskites have shown exceptional optoelectronic properties but poor stability. Conversely, oxide perovskites exhibit exceptional stability, yet hardly achieve their high photoelectric performances. For the first time, 2D perovskite LaNb₂O₇ may achieve the unity of high stability and high photoelectricity, high flexibility and high piezoelectricity.

Abstract

The unity of high-stability and high-performance in two-dimensional (2D) material devices has consistently posed a fundamental challenge. Halide perovskites have shown exceptional optoelectronic properties but poor stability. Conversely, oxide perovskites exhibit exceptional stability, yet hardly achieve their high photoelectric performances. Herein, for the first time, high-stability 2D perovskite LaNb₂O₇ (LNO) is engineered for high-performance wide-temperature UV light detection and human motion detection. High-quality LNO nanosheets are prepared by solid-state calcination and liquid-phase exfoliation technique, resulting in exceptional stability against high temperature, acid, and alkali solutions. As expected, individual LNO nanosheet device achieves ultra-wide temperature (80–780 K) and ultra-high (3.7 × 10⁴ A W⁻¹ at 780 K) UV light detection. Importantly, it shows high responsivity (171 A W⁻¹), extraordinary detectivity (4 × 10¹² Jones), fast speed (0.3/97 ms), and long-term stability under ambient conditions. In addition, wafer-scale LNO film devices can be used as pixel array detectors for UV imaging, and large-area flexible LNO film devices exhibit satisfactory photodetection performance after repeated bending tests. Interestingly, LNO nanosheets also exhibit distinct piezoelectric characteristics, which can serve as high-sensitivity stress sensors for human motion detection. These encouraging results may pave the way for more innovative advances in 2D perovskite oxide materials and their diverse applications.

Nature Physics, Published online: 02 August 2024; doi:10.1038/s41567-024-02602-0

A new ferroic-like phase has been discovered in highly doped superconducting cuprates. The existence of a well-defined order parameter on the supposedly disordered side of the phase diagram challenges the accepted theoretical framework.

A powerful strategy is developed to synthesize colloidal atomic-thin (≈1.6 nm) 2D CuS nanocrystals with significant photothermal conversion efficiency of up to 94.3%, and its rapid photothermal conversion mechanism is revealed. As an exceptional NIR-II photoacoustic contrast agent, the atomic-thin nanocrystals show excellent deep-tissue imaging capability of brain vascular nature.

Abstract

Exploring photothermal nanomaterials is essential for new energy and biomedical applications; however, preparing materials with intense absorption, highly efficient light-to-heat conversion, and enhanced photostability still faces the enduring challenge. Herein, the study synthesizes atomic-thin (≈1.6 nm) 2D copper sulfide (AT-CuS) plasmonic nanocrystals and find its extraordinary photothermal conversion efficiency (PCE) reaching up to 94.3% at the second near-infrared (NIR-II) window. Photophysical mechanism studies reveal that the strong localized surface plasmon resonance (LSPR) and out-of-plane size effect of AT-CuS induce strong optical absorption and non-equilibrium carrier scattering, resulting in a significant carrier-phonon coupling (7.18 × 10¹⁷ J K⁻¹ s⁻¹ m⁻³), ultimately enhancing the heat generation. Such a photothermal nanomaterial demonstrates at leastmes stronger NIR-II photoacoustic (PA) signal intensity than that of most commonly used miniature gold nanorods, together with greater biocompatibility and photo-/thermal-stability, enabling noninvasive PA imaging of brain microvascular in living animals. This work provides an insight into the rational exploration of superb NIR-II photothermal and photoacoustic agents for future practical utilizations.

In this work, the authors successfully demonstrate the effective reduction of contact resistance in MoS₂ n-and WSe₂ p-MOSFETs using semi-metallic PtSe₂ contacts. Furthermore, a vertically stacked n-MOS inverter employing two MoS₂ n-MOSFETs with semi-metallic PtSe₂ contacts is realized in wafer-scale, indicating the feasibility of 3D integration using semi-metallic PtSe₂.

Abstract

In this work, the potential of 2D semi-metallic PtSe₂ as source/drain (S/D) contacts for 2D material field-effect-transistors (FETs) through theoretical and experimental investigations, is explored. From the density functional theory (DFT) calculations, semi-metallic PtSe₂ can inject electrons and holes into MoS₂ and WSe₂, respectively, indicating the feasibility of PtSe₂ contacts for both n- and p-metal-oxide-semiconductor FETs (n-/p-MOSFETs). Indeed, experimentally fabricated flake-level MoS₂ n-MOSFETs and WSe₂ p-MOSFETs exhibit a significant reduction in contact resistance with semi-metallic PtSe₂ contacts compared to conventional Ti/Au contacts. To demonstrate the applicability for large-area electronics, MoS₂ n-MOSFETs are fabricated with semi-metallic PtSe₂ contacts using chemical vapor deposition-grown MoS₂ and PtSe₂ films. These devices exhibit outstanding performance metrics, including high on-state current (≈10⁻⁷ A/µm) and large on/off ratio (>10⁷). Furthermore, by employing these high-performance MoS₂ n-MOSFETs, vertically stacked n-MOS inverters are successfully demonstrated, suggesting that 3D integration of 2D material FETs is possible using semi-metallic PtSe₂ contacts.

Nano-pitch self-oxidized Al₂O₃/Al HKMG structures with a resolution of 150 nm are fabricated on 2D channel materials such as graphene, MoS₂, and WS₂ using an oxidation-assisted etching technique. This method allows for batch and high-yield production of top-gated 2D transistors without causing any additional damage to the 2D materials.

Abstract

2D materials with atomically thin nature are promising to develop scaled transistors and enable the extreme miniaturization of electronic components. However, batch manufacturing of top-gate 2D transistors remains a challenge since gate dielectrics or gate electrodes transferred from 2D material easily peel away as gate pitch decreases to the nanometer scale during lift-off processes. In this study, an oxidation-assisted etching technique is developed for batch manufacturing of nanopatterned high-κ/metal gate (HKMG) stacks on 2D materials. This strategy produces nano-pitch self-oxidized Al₂O₃/Al patterns with a resolution of 150 nm on 2D channel material, including graphene, MoS₂, and WS₂ without introducing any additional damage. Through a gate-first technology in which the Al₂O₃/Al gate stacks are used as a mask for the formation of source and drain, a short-channel HKMG MoS₂ transistor with a nearly ideal subthreshold swing (SS) of 61 mV dec⁻¹, and HKMG graphene transistor with a cut-off frequency of 150 GHz are achieved. Moreover, both graphene and MoS₂ HKMG transistor arrays exhibit high uniformity. The study may bring the potential for the massive production of large-scale integrated circuits using 2D materials.

Practical-level high-mobility indium oxide thin film transistors (TFTs) are realized by overcoming the gate bias instability. Only the indium oxide-based TFTs that are passivated with yttrium oxide or erbium oxide thin films do not exhibit threshold voltage shifts after negative/positive gate bias stress applications, likely due to the heteroepitaxial growth of the passivation film.

Abstract

Transparent oxide semiconductors (TOSs) based thin-film transistors (TFTs) that exhibit higher field effect mobility (µ _FE) are highly required toward the realization of next-generation displays. Among numerous types of TOS-TFTs, In₂O₃-based TFTs are the front-running candidate because they exhibit the highest µ _FE ≈100 cm² V⁻¹ s⁻¹. However, the device operation of In₂O₃ TFTs is unreliable; a large voltage shift occurs especially when negative gate bias is applied due to adsorption/desorption of gas molecules. Although passivation of the TFTs is used to overcome such instability, previously proposed passivation materials do not improve the reliability. Here, it is shown that the In₂O₃ TFTs passivated with Y₂O₃ and Er₂O₃ films are highly reliable and do not show threshold voltage shifts when applying gate bias. Positive and negative gate bias is applied to the In₂O₃ TFTs passivated with various insulating oxides and found that only the In₂O₃ TFTs passivated with Y₂O₃ and Er₂O₃ films do not exhibit threshold voltage shifts. It is observed that only the Y₂O₃ grew heteroepitaxially on the In₂O₃ crystal. This is the origin of the high reliability of the In₂O₃ TFTs passivated with Y₂O₃ and Er₂O₃ films. This finding accelerates the development of next-generation displays using high-mobility In₂O₃ TFTs.