Molecular junctions of metal-oxide-semiconductor and applications

Abstract

This invention relates to the field of semiconductor technology, specifically to a molecular junction of a metal oxide semiconductor and its applications, wherein the molecular junction is composed of oxygen vacancies and hydroxyl groups, which are bonded to the same metal atom to form an oxygen vacancy-hydroxyl metal oxide molecular junction (Oxygen vacancy-hydroxyl metal oxide, V). O (-M-OH). The molecular junction of this invention can achieve efficient hole injection / transmission, optimize interface band arrangement, and effectively suppress dark current.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically to a molecular junction of a metal oxide semiconductor and its applications. Background Technology

[0002] Metal oxide semiconductors (such as Ga2O3, ZnO, SnO2, InGaZnO, etc.) have important application prospects in ultraviolet-visible light detection, image sensing and other fields due to their wide bandgap, high mobility and good environmental stability. However, the core challenges in realizing high-performance metal oxide semiconductor (MOS) photoelectric response are: (1) Limited effective hole injection / transmission: Most MOS materials are essentially n-type or weakly p-type, lacking efficient and stable p-type doping methods, resulting in low hole collection efficiency and insufficient device responsivity; (2) Interface bandgap mismatch: There is often a significant bandgap at the metal electrode / MOS interface or heterojunction interface, forming a high hole injection barrier, which hinders the effective separation and collection of photogenerated carriers; (3) Significant dark current noise: Interface state defects and thermally excited carriers easily lead to high dark current, reducing the signal-to-noise ratio and detection sensitivity of the device. These factors seriously restrict the performance of MOS-based photodetectors in high-speed, high-sensitivity and low-power applications. Summary of the Invention

[0003] The purpose of this invention is to provide a molecular junction and application of metal oxide semiconductors, and to solve the technical problem of how to overcome the bottleneck of photoelectric response performance of metal oxide semiconductors in the prior art.

[0004] This invention discloses a molecular junction of a metal oxide semiconductor, wherein the molecular junction is composed of oxygen vacancies and hydroxyl groups, which are bonded to the same metal atom to form an oxygen vacancy-hydroxyl metal oxide molecular junction (Oxygen vacancy-hydroxyl metal oxide, V). O -M-OH).

[0005] Furthermore, the oxygen-vacancy hydroxyl metal oxide molecular structure (V O The structure of -M-OH is shown in formula (I): (I) Where: M is a metal atom, O is an oxygen atom, and V... O There is an oxygen vacancy, and H is a hydrogen atom.

[0006] Furthermore, the V O -M-OH molecular junctions exhibit p-type characteristics compared to intrinsic materials.

[0007] A method for preparing molecular junctions of metal-oxide-semiconductor (MODS) involves first preparing a precursor solution, then transferring the precursor solution and substrate material into a reaction apparatus for hydrothermal growth. After growth, the substrate is cooled, rinsed, and dried. The resulting nanorods are then annealed to obtain crystalline nanorods. Subsequently, the surface of the nanorods is irradiated with an ultrafast laser in a hydrogen-containing environment to obtain V-containing nanorods. O Nanorod samples with -M-OH molecular junctions.

[0008] Furthermore, the nanorods are α-Ga2O3 nanorods.

[0009] Furthermore, prior to growth, the substrate material is sequentially cleaned in an ultrasonic bath with ethanol, acetone, and deionized water, and then dried under a nitrogen flow.

[0010] Furthermore, the precursor solution is prepared by using Ga(NO3)3 It can be obtained by dissolving 9H2O and NaOH in deionized water.

[0011] Furthermore, the Ga(NO3)3 The molar ratio of 9H2O to NaOH is 3.9-4.5:35-40.

[0012] Furthermore, the precursor solution has a pH of 4-6.

[0013] Furthermore, the hydrothermal growth temperature is 150~200℃.

[0014] Furthermore, the temperature for drying after rinsing is 25-60°C.

[0015] Furthermore, the annealing is performed by heating and annealing at 350-500°C in a vacuum tube furnace for 2-6 hours.

[0016] An application of a molecular junction of a metal-oxide-semiconductor for improving carrier transport in photoelectric detectors, display devices, or transistors.

[0017] Furthermore, it is used for solar-blind ultraviolet detection of gallium oxide.

[0018] By improving the dynamics of photogenerated carriers, the photoresponse current is increased and the dark current is reduced, making it potentially suitable for efficient self-powered detection applications in underwater environments such as seawater. The improved gallium oxide material also exhibits a better signal-to-noise ratio, enabling its use in more extreme detection environments.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. The molecular junction of this invention can achieve efficient hole injection / transmission, optimize the interface band arrangement, and effectively suppress dark current.

[0020] 2. The molecular junction of this invention can achieve efficient and controllable carrier injection and transport. By constructing a self-assembled molecular junction on the surface of a metal oxide semiconductor, a high-mobility hole transport channel is formed, which significantly reduces the hole injection barrier. Compared with unmodified devices, the photogenerated carrier efficiency is significantly improved. At the same time, the atomically flat interface of the molecular junction ensures the uniformity and stability of carrier transport across the interface, fundamentally solving the problem of low hole collection efficiency and insufficient responsivity caused by the difficulty in realizing the p-type characteristics of materials.

[0021] 3. The molecular junction of this invention can actively control the interfacial band structure, optimize photogenerated carrier separation, and the designability of the molecular junction's energy levels endows it with interfacial band engineering capabilities. This structure can dynamically match the Fermi level of metal electrodes or heterojunctions, eliminating the high injection barrier found in traditional devices. Experiments show that the charge resistance at the interface is reduced, significantly improving photoresponse capability.

[0022] 4. The molecular junction of this invention effectively suppresses dark current noise and improves overall detection performance. The molecular junction can chemically passivate dangling bonds and defect states on the surface of metal oxides. This characteristic reduces the device's dark current density to a minimum and increases the detectivity by orders of magnitude, laying the foundation for high-sensitivity, low-power photoelectric detection applications. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 V in gallium oxide is an example of V in Example 1 O -M-OH molecular structure diagram.

[0025] Figure 2 The V calculated based on density functional theory in Example 1 is... O The formation energy of the -M-OH molecular structure is calculated relative to the original defect-free surface (set to 0 eV as a reference value).

[0026] Figure 3 This is a schematic diagram of the band structure of the intrinsic α-Ga2O3 surface structure calculated based on density functional theory in Example 1.

[0027] Figure 4 This is the result of calculation based on density functional theory in Example 1, which has V O A schematic diagram of the band structure of the α-Ga2O3 surface.

[0028] Figure 5This is the result of calculation based on density functional theory in Example 1, which has V O A schematic diagram of the band structure of the α-Ga2O3 surface structure of the -M-OH molecular junction.

[0029] Figure 6 This is a Fourier transform infrared spectrum of a metal oxide semiconductor before and after the preparation of its molecular junction, as shown in Example 1.

[0030] Figure 7 This is an electron paramagnetic resonance spectrum of a metal oxide semiconductor before and after the preparation of a molecular junction, as shown in Example 1.

[0031] Figure 8 This is a solar-blind ultraviolet detector with a molecular junction package of metal-oxide-semiconductor as described in Example 1, showing the photoresponse current diagram for four on / off cycles under a wavelength of 254 nm and a bias voltage of 0 V.

[0032] Figure 9 Example 1 shows a solar-blind ultraviolet detector with a molecular junction package of metal-oxide-semiconductor. Compared with U-NRA, L-NRA has a faster rise time (C2) and fall time (C4) at a wavelength of 254nm and a bias voltage of 0V.

[0033] Figure 10 Example 1 describes a solar-blind ultraviolet detector using a metal-oxide-semiconductor molecular junction package, exhibiting responsivity (R) and detectivity ratio (R / V) at a wavelength of 254 nm and a bias voltage of 0 V. D *).

[0034] Figure 11 Example 1 describes a solar-blind ultraviolet detector with a molecular junction packaged metal-oxide-semiconductor, exhibiting a photo-dark current ratio at a wavelength of 254 nm and a bias voltage of 0 V.

[0035] Figure 12 Schematic diagram of photoelectrochemical response mechanism under illumination. (A) U-NRA band structure. (B) L-NRA band structure. (C) Dynamics of photogenerated carriers in U-NRA. (D) Dynamics of photogenerated carriers in L-NRA.

[0036] Figure 13 Electrochemical impedance spectroscopy (EIS) spectra of a metal-oxide-semiconductor molecular junction before and after fabrication in Example 1, wherein... R S Series resistor; R CT and CPE CT Interface unit. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0038] Example 1 This embodiment discloses a molecular junction of a metal-oxide-semiconductor and its application, including the following steps: 1) V O Synthesis of -M-OH molecular knots: This embodiment uses α-Ga2O3 nanorods as an example to introduce a method for preparing V using ultrafast laser irradiation. O The method of -M-OH molecular junction. α-Ga2O3 nanorods were synthesized using a fluorine-doped tin oxide (FTO) substrate via a hydrothermal process. Prior to growth, the FTO substrate (10 mm × 20 mm × 2.1 mm) was sequentially cleaned in an ultrasonic bath with ethanol, acetone, and deionized water for 10 minutes each, and then dried under a nitrogen flow. This was achieved by using 0.3 M Ga(NO3)3... A precursor solution (pH≈5) was prepared by dissolving 9H₂O and 0.075 M NaOH in deionized water. The solution and a clean FTO substrate were transferred to an autoclave and heated to 180 °C to promote the hydrothermal growth of GaOOH nanorods. After cooling, the sample was rinsed with deionized water and dried at 60 °C. The resulting GaOOH nanorods were then annealed at 400 °C for 4 hours in a vacuum tube furnace to obtain crystalline α-Ga₂O₃ nanorods. Subsequently, the nanorod surface was irradiated with an ultrafast laser of appropriate parameters in a hydrogen-containing environment to obtain V-containing nanorods. O α-Ga2O3 nanorod samples with OV-M-OH molecular structures were obtained. The stable OV-M-OH molecular structure was determined by density functional theory, and the chemical composition was confirmed by Fourier transform infrared spectroscopy and electron paramagnetic resonance.

[0039] 2) V O Characterization of -M-OH molecular junctions: Density Functional Theory (DFT) is a numerical method widely used in quantum chemical calculations to study the electronic structure and stability of molecules and materials. By solving the Schrödinger equation, DFT can predict key properties of molecules, such as geometry, energy, electron distribution, and vibrational frequencies, thereby assessing their structural stability and reactivity. To perform DFT calculations, use a common platform like Gaussian or VASP, set the calculation method and parameters in the input file, submit the molecular structure file, and run the optimized calculation task. After the calculation is complete, the stability and electronic properties of the molecule can be determined by analyzing parameters such as total energy, band structure, and vibrational frequencies.

[0040] Based on V O To obtain experimental evidence of the coexistence of V and OH groups, we systematically studied the V group using density functional theory (DFT). O The stability and electronic structure of the -Ga-OH molecular junction. After sufficient relaxation of the atomic structure, we calculated the formation energy of various possible configurations ( Figure 2 This was used to identify the most likely defect structures on the surface. The results showed that the most stable configuration was a hydroxyl group bridging two adjacent oxygen vacancies with Ga atoms. The formation energy of this configuration was significantly lower than that of the terminal V... O -Ga-OH configuration and V-free O The Ga-OH structure confirmed the crucial role of oxygen vacancies in stabilizing the molecular structure. This cooperative stabilization mechanism likely stems from two factors: the positively charged V... O This provides effective electronic compensation for the negatively charged OH group, creating an electrically favorable local environment. Simultaneously, vacancy-induced atomic relaxation produces coordinate-unsaturated Ga atoms, which become highly reactive anchoring sites. In the bridging configuration, the distance between the hydroxyl oxygen atom and the neighboring Ga atom is closer to the typical Ga-O bond length in the Ga₂O₃ bulk phase, while this distance is significantly larger in the terminal configuration, further confirming from a geometric perspective that the bridging hydroxyl configuration has higher stability.

[0041] For the original V O The density of states (DOS) calculations of the structure confirm that it has n-type characteristics, exhibiting deep donor states within the band gap. Figures 3-4 In contrast, the complete V O The density of states of the Ga-OH junction reveals the phenomenon of electronic reconstruction. O The synergistic effect between the oxygen group and the -OH group leads to the saturation of dangling bonds formed by oxygen vacancies, effectively suppressing n-type conductivity. Crucially, this synergistic effect collectively generates shallow acceptor levels above the highest valence band level. Figure 5 This newly formed shallow energy level becomes a highly efficient hole generation center. Under photoexcitation, electrons from the valence band apex are raised to this acceptor level, occupying them while leaving mobile holes in the valence band. This dual mechanism—deep n-type donor cooperative passivation and shallow p-type acceptor synchronous generation—makes V O -Ga-OH junctions become robust functional units, capable of actively constructing p-type conductive paths within Ga2O3.

[0042] II. V O Determination of the enhanced photoelectric detection response of -M-OH molecular pairs Photoelectric detection response test at 254nm wavelength light, 400μW / cm 2Under 0V bias conditions, an electrochemical workstation (CH660E) was used to collect electrical signals. The responsivity (R) and detectivity ratio (R / R) were then used as parameters. D *) The photocurrent-dark current ratio is quantitatively analyzed, and the expressions are as follows: , , ,in Indicates the photoresponse current. Indicates dark current. Indicates the incident light power. Indicates the photosensitive area. e It represents the elementary charge.

[0043] Experimental results are as follows Figure 6-10 As shown. For ease of distinction, the samples before and after treatment are named U-NRA and L-NRA, respectively. It can be observed that the treated sample exhibits significant changes in oxygen vacancy content and hydroxyl functional group bonding. Combined with the stable structure predicted by density functional theory based on the minimum formation energy, this confirms the presence of V... O The successful preparation of the -M-OH molecular junction. Next, photoelectric detection response and electrochemical impedance spectroscopy were performed on the sample. For example... Figure 8 As shown, under a 0V bias voltage, it is irradiated with 254 nm monochromatic light (400 μW / cm). 2 L-NRA devices achieve 3.47 μA / cm 2 The photocurrent density, compared to the U-NRA reference value (0.97 μA / cm²), is... 2 It improves by 373%, and compared to U-NRA, it has V O The L-NRA sample with the -M-OH molecular junction exhibits a higher photoresponse current under the same conditions, which is attributed to V O The band structure modulation properties of the -M-OH molecular junction, from Figure 12 It can be seen that the material surface passes through V O The -M-OH junction enhances hole conductivity and combines with the Ga2O3 bulk system, which generates excess free electrons due to intrinsic oxygen vacancies, to form a new vertically aligned pn junction. Under illumination, this field actively guides photogenerated carriers, drives charge separation, and provides a pathway for hole injection into the electrolyte, thereby accelerating reaction kinetics, optimizing carrier transport channels, and enhancing the kinetics of photogenerated carriers.

[0044] In addition, such as Figure 9 and Figure 11 As shown, molecular node modification exhibits significant superiority in key device performance. The response speed of L-NR is significantly improved, with rise time and decay time of 0.17 seconds and 0.10 seconds, respectively, far faster than U-NR (0.41 seconds and 0.17 seconds, respectively). Figure 9The responsiveness (R) is improved by 373%, reaching 30.66 mA / W. Figure 10 Meanwhile, the detectivity (D*) increased by 645% to 5.93 × 10⁻⁶. 10 Jones, the photocurrent to dark current ratio (PDCR) increased by 1115% to 1469.34 ( Figure 10 and Figure 11 The synergistic improvement of these key indicators confirms that the molecular junction is the fundamental source of performance enhancement. Its role can be understood as integrating a carrier management unit: the built-in electric field enables rapid extraction and transport of photogenerated carriers (shortening response time), while the customized band structure promotes efficient separation and collection of positive and negative electrons (improving R and D*). Simultaneously, the modified interface suppresses recombination and dark current, achieving a high PDCR value. Essentially, the molecular junction optimizes the entire photodetection process by actively modulating the interface environment, overcoming the limitations of passive doping technology, resulting in improved responsivity (R), detectivity ratio (D*), and so on. D *), The ratio of light to dark current both indicate that V O -M-OH molecular junctions can significantly improve the optical detection performance of devices.

[0045] To understand the performance enhancement mechanism, we delved into the interface charge transfer efficiency.

[0046] from Figure 12 It can be seen that the charge resistance at the interface is reduced, which significantly improves the photoresponse capability.

[0047] Electrochemical impedance spectroscopy (EIS) revealed a key difference: the L-NR material exhibited a significantly reduced semicircle in the mid-frequency region. Figure 13 This indicates a significant improvement in charge transfer efficiency at the electrode-electrolyte interface. Equivalent circuit fitting confirms a substantial reduction in the charge transfer resistance (RCT) of the L-NRA, while its series resistance (RS) is comparable to that of the U-NRA. This directly demonstrates that the VO-M-OH molecular junction (rather than bulk properties) is the key factor in reducing the interfacial energy barrier and promoting charge transport.

[0048] The above are the embodiments listed in this example. However, this example is not limited to the optional embodiments described above. Those skilled in the art can arbitrarily combine the above methods to obtain other various embodiments. Anyone can derive other various forms of embodiments based on the inspiration of this example. The above specific embodiments should not be construed as limiting the scope of protection of this example. The scope of protection of this example should be determined by the claims, and the specification can be used to interpret the claims.

Claims

1. A molecular junction of a metal-oxide-semiconductor, characterized in that: The molecular junction consists of oxygen vacancies and hydroxyl groups, which are bonded to the same metal atom, forming an oxygen-vacancy-hydroxyl metal oxide molecular junction V. O -M-OH.

2. The molecular junction of a metal-oxide-semiconductor according to claim 1, characterized in that: The molecular structure of the oxygen-vacancy hydroxyl metal oxide is shown in formula (I): （Ⅰ） Where: M is a metal atom, O is an oxygen atom, and V... O There is an oxygen vacancy, and H is a hydrogen atom.

3. The molecular junction of a metal-oxide-semiconductor according to claim 1, characterized in that: The V O -M-OH molecular junctions exhibit p-type characteristics compared to intrinsic materials.

4. A method for preparing a molecular junction of a metal-oxide-semiconductor according to any one of claims 1-3, characterized in that: First, a precursor solution is prepared. Then, the precursor solution and substrate material are transferred to a reaction apparatus for hydrothermal growth. After growth, the nanorods are cooled, rinsed, and dried. The resulting nanorods are then annealed to obtain crystalline nanorods. Subsequently, the surface of the nanorods is irradiated with an ultrafast laser in a hydrogen-containing environment to obtain V-containing nanorods. O Nanorod samples with -M-OH molecular junctions.

5. The method for preparing a molecular junction of a metal-oxide-semiconductor according to claim 4, characterized in that: The nanorods are α-Ga2O3 nanorods.

6. The method for preparing a molecular junction of a metal-oxide-semiconductor according to claim 4, characterized in that: The precursor solution is prepared by using Ga(NO3)3 It can be obtained by dissolving 9H2O and NaOH in deionized water.

7. The method for preparing a molecular junction of a metal-oxide-semiconductor according to claim 6, characterized in that: The Ga(NO3)3 The molar ratio of 9H2O to NaOH is 3.9-4.5:35-40.

8. The method for preparing a molecular junction of a metal-oxide-semiconductor according to claim 4, characterized in that: The precursor solution has a pH of 4-6; And / or the temperature for drying after rinsing is 25-60°C; And / or the annealing is performed by heating and annealing at 350-500°C for 2-6 hours in a vacuum tube furnace.

9. The application of a molecular junction of a metal-oxide-semiconductor according to any one of claims 1-3 or a molecular junction prepared by the method for preparing a molecular junction of a metal-oxide-semiconductor according to any one of claims 4-8, characterized in that: Used to improve carrier transport in photoelectric detectors, display devices, or transistors.

10. The application according to claim 9, characterized in that: Solar-blind ultraviolet detection for gallium oxide.

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