Description:Form 2

THE PATENT ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)

“A PROCESS OF PREPARATION OF ANODIC ORTHORHOMBIC PHASE MOLYBDENUM TRIOXIDE (α-MoO3) RESISTIVE SWITCHING MEMRISTIVE ELEMENT”

in the name of PONDICHERRY UNIVERSITY an Indian National having address at, R. VENKATARAMAN NAGAR, KALAPET, PUDUCHERRY, PUDUCHERRY, PUDUCHERRY – 605014, INDIA.

The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION:

The present invention relates to the field of electronic devices, and more specifically to memristive materials and their applications in resistive switching devices. More particularly the present invention relates to method for fabricating an anodic orthorhombic phase molybdenum trioxide (α-MoO3) resistive switching memristive device and product thereof.

BACKGROUND OF THE INVENTION:

The development of memristive devices has significantly progressed with the innovative use of metal oxides, known for their unique electrical properties and suitability for memory applications. Metal oxides have become critical materials in the fabrication of memristors, which are resistive switching devices fundamental to the development of non-volatile memory and neuromorphic computing systems. Various metal oxides, including titanium dioxide (TiO2), zinc oxide (ZnO), and copper oxide (CuO), have been investigated for their resistive switching capabilities. These studies demonstrate various switching mechanisms, including unipolar and bipolar switching, illustrating the diversity of electrochemical processes involved in resistive switching.

The rapid advancement of electronic technologies has significantly increased the demand for efficient and reliable memory devices. Traditional memory technologies, such as dynamic random-access memory (DRAM) and flash memory, have inherent limitations, including slow switching speeds, high power consumption, and volatility in the case of DRAM. As a result, there is a pressing need for innovative materials and devices that can overcome these challenges and facilitate the development of next-generation memory and computing systems. A memristive element, or memristor, is a fundamental passive two-terminal electronic device that exhibits a unique relationship between the electric charge (current) passing through it and the magnetic flux linkage (voltage) across it. First conceptualized by Leon Chua in 1971, the memristor is regarded as the fourth fundamental circuit element, alongside resistors, capacitors, and inductors.

Memristors have emerged as a promising paradigm shift in the field of electronics. As a class of non-volatile memory devices, memristors possess the unique ability to retain information without a continuous power supply, thereby offering significant advantages in terms of energy efficiency and data retention. Their resistive switching behaviour, influenced by the history of applied voltage and current, allows for versatile applications in data storage and processing.

Among the various materials investigated for memristive applications include metal oxides, organic materials, perovskites, bio materials, two dimensional materials, and transition metal dichalcogenides, metal oxides have shown considerable potential due to their suitable electrical and structural properties which can be engineered to optimize their resistive switching properties. This innovative technology has the potential to revolutionize data storage, computation, and the development of intelligent systems.

The current state of the art in memristor technology showcases a variety of metal oxides, including titanium dioxide (TiO2), zinc oxide (ZnO), and tantalum oxide (Ta2O5), recognized for their effective resistive switching capabilities. These materials have been extensively studied and utilized in various device configurations for applications in non-volatile memory, neuromorphic computing, and advanced electronic systems. Fabrication methods such as chemical vapor deposition (CVD) and physical vapor deposition (PVD) are frequently employed to achieve the desired material properties, facilitating the development of high-performance memristors. However, these advanced synthesis techniques often necessitate highly controlled environments and expensive machinery, which can limit the scalability and accessibility of such devices for widespread application.

Despite the advancements in memristor technology, there are several significant drawbacks associated with the existing state of the art. The sophisticated synthesis methods, such as CVD and PVD, typically result in high production costs and complex operational requirements. Additionally, these methods can yield inconsistencies in oxide layer quality and uniformity, leading to the incorporation of impurities that adversely affect the electrical performance and reliability of the resulting memristors. The reliance on specialized equipment further restricts optimization, as many researchers may lack access to the necessary facilities. Moreover, achieving high-purity oxide layers remains a challenge, which is critical for maximizing device efficiency and lifespan. These limitations highlight a need for a more effective and scalable fabrication approach to enhance the performance of memristor devices. Hence an attempt has been made to fabricate a memristive device which is devoid of above said drawbacks.

OBJECT OF THE INVENTION:

The main object of the present invention is to fabricate a memristive device.

Another objectives of the present invention are

a. To provide a cost-effective and less material requiring method of synthesizing molybdenum trioxide (α-MoO3) using anodization for memristive material that reduces the overall production costs compared to traditional methods
b. To enable versatile adjustments in the anodization parameters (e.g., voltage, duration, electrode materials) to tailor the electrical properties and performance of the anodized α-MoO3 memristor for specific applications and requirements.
c. To provide a scalable approach to the fabrication of anodized α-MoO3 memristors, allowing for integration into mass production processes for various electronic applications, such as memory storage and neuromorphic computing.
d. To explore and harness unique material properties of anodized α-MoO3, such as high surface area and beneficial electrochemical characteristics, to enhance the device performance and operational stability
e. To ensure the anodized α-MoO3 memristor can be easily integrated into existing electronic circuitry, promoting adoption in current technological frameworks without requiring major revisions to current manufacturing processes.

BRIEF DESCRIPTION OF DRAWINGS:

Figure 1 depicts the Schematic flowchart for anodization including pre and post processing of samples

Figure 2 depicts the (a) Graphical representation of the Electrochemical Anodization process with factors influenced in anodization, (b) real camera image of the anodization reactor setup, (c) comparison of optical camera photographs of the Mo Foil under anodization, annealing, and top electrode deposited (Sputtered)

Figure 3 depicts the X- Ray Diffraction (XRD) pattern of the annealed Molybdenum foils (450oC for 2hours) confirming the presence of pure orthorhombic(α-MoO3) crystalline structures comparing with pristine anodized (amorphous in nature) and pure Mo foil.

Figure 4 depicts Raman spectroscopic analysis of the samples annealed under different Temperatures (150oC – 550oC) with all the modes

Figure 5 depicts the Field Emission scanning electron microscopy (FESEM) images of the a) & b) anodized α-MoO3 layer (annealed- 450oC/2hr) under different magnification, revealing the microstructural features such as its porous morphology and average particle size, which are instrumental in enhancing the device's charge transport properties. c) the surface of the silver deposited α-MoO3 layer & d) revels the cross sectional FESEM image of the Ag/ α-MoO3/Mo resistive switching device.

Figure 6 depicts graphical illustration of the Metal-Insulator-Metal (MIM) configuration of the memristive device, measurement consisting of the bottom Mo foil electrode, the anodized α-MoO3 active middle layer, and the top metallic silver (Ag) electrode. This arrangement is crucial for achieving the desired resistive switching measurement taken in the electrochemical workstation

Figure 7 depicts the electrical performance of the active device for 30 consecutive cycles (a) Current Vs Voltage in real scale, (b) Log-log plot of the Current vs voltage response of Mo/α-MoO3/Ag switching device.

Figure 8 depicts (a) the endurance (30 Cycles) and (b) retention(1200s) properties of the active device recorded with a read voltage of Vread = -0.4V. The ON/OFF ratio was marked for 30 cycles

SUMMARY OF THE INVENTION:

The present invention discloses an innovative memristive device utilizing anodic molybdenum trioxide (α-MoO3) as a high-performance resistive switching material. This memristor exhibits exceptional bipolar resistive switching behaviour, characterized by distinct high-resistance (HRS) and low-resistance (LRS) states, controlled by the application of SET and RESET voltages, and demonstrating a high ON/OFF ratio of approximately 50. The device boasts excellent retention properties, maintaining resistance states for over 10^3 seconds, alongside reliable operation over 30 switching cycles, showcasing stability and durability. The fabrication involves a simple electrochemical anodization process using molybdenum (Mo) foil as the substrate, with subsequent thermal annealing treatments to enhance crystallinity and optimize electrochemical properties. Structured in a Metal-Insulator-Metal (MIM) architecture, the configuration employs Mo foil as the bottom electrode and metallic silver (Ag) as the top, ensuring effective charge transport. The advantages of this memristive device include low operating voltages (0.4 V for SET and -0.6 V for RESET), resulting in reduced energy consumption compared to conventional memory technologies. The anodization process is environmentally friendly, compared to more complex chemical methods, supporting sustainable manufacturing practices. Overall, the efficiency of the memristive device reflects its ability to deliver reliable performance while consuming minimal power, positioning it as a competitive alternative to traditional non-volatile memory solutions. Its unique properties support potential applications in neuromorphic computing, emphasizing the ability to emulate biological synaptic functions and advance the development of intelligent electronic systems.
DETAILED DESCRIPTION OF THE INVENTION:

The present invention discloses a method for fabricating an anodic orthorhombic phase molybdenum trioxide (α-MoO3) resistive switching memristive device and product thereof.

The invention relates to developing and applying microstructured anodic Molybdenum Trioxide (α-MoO3) as a resistive switching material for memristive devices fabricated through a low-cost anodization process in organic based electrolyte. The memristive device has a Metal-Insulator-Metal (MIM) structure. The device employs Molybdenum (Mo) foil as base electrode, anodic orthorhombic phase α-MoO3 crystal as switching layer, and a PVD deposited Silver (Ag) as top electrode.

Potentiostatic Anodization: Electrochemical anodization process was conducted on a molybdenum foil using the Potentiostatic method in a fluorine-based organic electrolyte. The fabrication scheme was laid out in the flowchart (Fig.1). The molybdenum foil was polished to a mirror finish with various grit ranges (100 to 2000) and cleaned with a soap solution, acetone, ethanol, and distilled water in an ultrasonic bath for 10 minutes each, followed by air drying. The anodization reactor setup comprised a two-electrode configuration with the molybdenum foil (1cm x 2cm) serving as the working electrode (anode) and Platinum (Pt) mesh as the counter electrode (cathode). The distance between the electrodes was maintained at a constant 2.5 cm. The electrolyte was prepared by adding 0.1M NH4F in a 5%/95% vol/vol water-ethylene glycol solution. A constant voltage of 40V was applied for 1 hour at a stable anodization temperature of 23 °C (±1 °C) to ensure uniform film formation. The anodized samples were cleaned using ethanol and deionized water and then dried in air. The complete anodization process was adapted and modified from various prior reports. As the anodized pristine samples were amorphous, they were transformed into crystalline (orthorhombic) structures through thermal annealing with 450 °C, and 550 °C for 2 hours, with a heating rate of 5 °C min−1 in a muffle furnace. From the optical photographs of the Mo foil, we could the see the transition and formation of oxide layer as in fig.2

Fabrication of Memristive Element: The Resistive switching phenomena of obtained molybdenum oxide was studied using a Metal/ Insulator(semiconductor)/Metal (MIM) sandwich configuration. Anodic α-MoO3 as the active semiconducting layer, base molybdenum (Mo) foil as the bottom electrode, and Silver (Ag) as a top electrode. The Ag top electrodes were patterned with a shadow mask on the oxide layer using DC magnetron sputtering (PLASSYS MP300, France make) using an Ag metal target (99.9%) with working pressure of 7.3 mTorr in 10 sccm in high purity (99.99%) Argon (Ar) gas with deposition time of 9 min under room temperature. The obtained PVD Ag thin film was uniform with thickness around ~600 nm and each electrode have area of cross section of 1.2 mm x 1.2 mm. Thus, the resulted top Ag contact was good-quality and used for electrical measurement.

Characterization studies of the Molybdenum Trioxide Anodic layers

The morphological characterization was performed using Field Emission Scanning electron microscopy (FE-SEM) under various magnifications using Carl Zeiss SUPRA 55, NTS GMBH, Germany. The X-ray Diffraction analysis was recorded for the confirmation of the orthorhombic phase of the MoO3 from the samples annealed at different temperatures and timings using Powder diffraction X-ray beam diffractometer (ARL EQUINOX 3000, Thermofisher Scientific, USA make) with Cu-Kα1 radiation (λ = 1.5406 Å) working under 40KV and 30mA and equipped with a CPS detector. To study the molecular arrangement of MoO3, RAMAN spectra were recorded by a confocal micro-Raman spectrometer (In Via, Renishaw, UK), using an argon ion laser emitting at 532 nm for the spectral range of 50 to 1500 cm-1.

Electrical Characterization of the Memristive Element

The electrical I-V characterization was done for the sample anodized for 60 minutes with 40V and annealed under 450 °C for 2h with sample working area of 1.2mm x 1.2mm. The Switching properties data were recorded and analyzed using an electrochemical workstation (Metrohm, Autolab PGSTAT302N) with a two-electrode configuration by connecting Anode (Ag Top Electrode) probe to Working Electrode (WE) and Sens Electrode (SE) and Cathode (Mo Bottom Electrode) probe to Counter Electrode (CE) and Reference Electrode (RE) respectively, as shown in the schematic setup (Fig 2a.). The Electrical measurement was done using Cyclic voltammetry (CV) module in Potentiostatic mode by sweeping the DC voltages under different potential windows for several cycles. The Bias voltage was applied to the top Ag electrode and Mo foil was grounded (common ground configuration).as in fig.5. To avoid electrical breakdown of the device, the compliance current (Icc) was kept at 100mA. The measurement data was analysed using Metrohm NOVA 2.1 software. All experiments were performed and measured at room temperature under air ambient conditions.

Results & discussion: X-ray diffraction (XRD) analysis is a critical technique employed to investigate the crystallographic structure and phase composition of anodic molybdenum trioxide (α-MoO3) in the fabrication of memristive devices. In this study, XRD was utilized to determine the crystallinity, phase purity, and structural properties of the α-MoO3 layer formed during the anodization process. The XRD patterns in fig.3. revealed distinct diffraction peaks that correspond to the orthorhombic phase of MoO3, confirming the successful transformation from an amorphous state to a crystalline structure upon thermal annealing. Furthermore, the analysis provided quantitative data on crystallite size, dislocation density, and lattice micro strain, which are essential parameters influencing the electrical performance of the memristor. By applying the Debye-Scherrer equation to the prominent peaks in the XRD spectrum, the crystallite size was calculated, demonstrating that optimal annealing conditions led to improved crystallinity and enhanced charge transport properties. The XRD results underscore the importance of phase purity and structural integrity in optimizing the performance of α-MoO3 memristive devices, ultimately contributing to their resilience and efficiency in resistive switching applications.

Raman spectroscopy analysis was conducted to gain insights into the molecular structure and bonding characteristics of anodic molybdenum trioxide (α-MoO3) synthesized for memristive applications. This technique utilizes inelastic scattering of monochromatic light, typically from an argon ion laser, to probe vibrational modes within the material. The Raman spectra from fig 4. revealed several distinct peaks corresponding to various vibrational modes associated with the Mo-O bonds in the α-MoO3 lattice. Notably, a significant peak observed at approximately 995 cm⁻¹ was attributed to the stretching mode of terminal oxygen (Mo=O), indicative of the formation of the orthorhombic phase of MoO3. Additional peaks at 819 cm⁻¹ and 666 cm⁻¹ were associated with the stretching modes of double and triple coordinated oxygen atoms, respectively, illustrating the intricate bonding environment within the crystalline structure. Analysis of the Raman spectrum suggested that samples annealed at temperatures above 350 °C exhibit a well-defined crystalline structure, as evidenced by the emergence of distinct peaks, whereas samples below this temperature remained amorphous. This study of Raman spectroscopy confirms the successful synthesis of α-MoO3 and underscores the relationship between its structural features and the resultant electrical properties, which are pivotal for the functionality of memristive devices.

Field Emission Scanning Electron Microscopy (FESEM) studies were conducted to thoroughly investigate the surface morphology and microstructural characteristics of anodic molybdenum trioxide (α-MoO3) synthesized for memristive applications. The high-resolution electron micrographs in fig 5a & 5b. obtained from the FESEM analysis revealed the formation of hierarchical microgranular structures, which are essential for optimizing the electrical performance of the memristive device. These micro grains exhibited a well-defined morphology with uniform porosity and a high surface-to-volume ratio, significantly enhancing the effective charge transport during resistive switching. The images also indicated that the anodization process led to a homogeneous distribution of these microstructures across the substrate, which is critical for achieving consistent device performance. Additionally, particle size analysis revealed an average nanoplatelet diameter of approximately 774 nm, indicating a relatively uniform size distribution that contributes to the device's stability. The cross-section electron imaging reveals the metal/semiconductor/metal stack of the resistive switching element. Overall, the FESEM studies provided essential insights into the morphological features of anodized α-MoO3

Electrical characterization of the anodic molybdenum trioxide (α-MoO3) memristor was conducted to systematically analyse its resistive switching properties and overall performance. The characterization involved current-voltage (I-V) measurements, where the device exhibited distinct hysteresis behaviour, indicative of its bipolar resistive switching capabilities as shown in fig 7a & 7b. Specifically, the device demonstrated a SET voltage of approximately 0.4 V and a RESET voltage of about -0.6 V, allowing for effective transitions between the high-resistance state (HRS) and low-resistance state (LRS) yielding an ON/OFF ratio of approximately 50. Additional tests assessed the device's endurance, revealing that it maintained stable performance over more than 30 switching cycles as in fig.8a. Retention tests confirmed that the memristor preserved its defined resistance states for durations exceeding 10^3 seconds as in fig. 8b, emphasizing its suitability for non-volatile memory applications. These results indicate that the α-MoO3 memristor displays promising reliability and efficiency, making it a suitable candidate for advanced electronic applications, including next-generation memory devices and neuromorphic computing. Overall, the electrical characterization provides valuable insights into the unique switching mechanisms of the anodic α-MoO3 memristor, contributing to its potential for practical use in innovative electronic systems.

ADVANTAGES

1. The electrochemical anodization process used for synthesizing α-MoO3 is straightforward, cost-effective, and generates minimal waste, aligning with sustainable manufacturing practices.
2. The unique microstructural characteristics of anodized α-MoO3, including high surface area and porosity, lead to improved charge transport properties, enhancing overall device performance.
3. The device demonstrates robust bipolar resistive switching behaviour, enabling efficient toggling between high-resistance (HRS) and low-resistance (LRS) states,
4. The memristor exhibits a high ON/OFF ratio of approximately 50, allowing for effective data differentiation and enhanced signal integrity in memory applications.
5. The device operates at minimal SET and RESET voltages (0.4 V and -0.6 V), which significantly reduces power consumption and minimizes heat generation during operation. Its low-power operation makes it an environmentally friendly alternative to conventional memory technologies, contributing to energy savings in electronic devices.
6. The ability to maintain resistance states over an extended duration (more than 10^3 seconds) ensures reliable data retention, critical for non-volatile memory solutions
7. The anodization technique allows for uniform and scalable fabrication of memristive devices, making it suitable for integration into advanced electronic circuits and systems.
8. The exotic properties of α-MoO3 open avenues for various applications beyond traditional memory, including neuromorphic computing and artificial synaptic emulation, and also sensing technology which may enable more advanced computation architectures.
9. Patterned anodization can be facilitated to integrate into electronic circuits, simplifying the manufacturing process and reducing production costs.
10. Enhanced material control through anodization allows for easy doping and composite creation, improving memristor performance characteristics.
The invention is of a scalable and cost-effective anodization process for synthesizing high-purity anodic molybdenum trioxide (α-MoO3) as a memristive material is novel in the context of existing memristor fabrication techniques. While various metal oxides have been employed previously in memristors, the specific use of anodic α-MoO3, achieved through an electrochemical anodization approach, represents a unique contribution to the field. This method allows for the creation of uniform oxide layers with controlled morphology and enhanced electrical performance, distinguishing it from traditional synthesis techniques such as chemical vapor deposition (CVD) and physical vapor deposition (PVD).
The non-obviousness of the invention lies in its application of a relatively simple anodization technique to create a material that not only meets the rigorous performance requirements of memristors but also does so in a way that is more accessible and cost-effective than existing methods. Prior approaches have often overlooked the potential of anodic metal oxides for use in high-performance neuromorphic devices. The decision to employ anodized α-MoO3 in memristors is non-trivial, as it combines an established electrochemical technique with advanced electronic applications, demonstrating an inventive leap rather than an incremental improvement.

The invention step comprises the development and optimization of the anodization process to produce α-MoO3 layers with high purity and consistent quality. This encompasses specific parameters such as electrolyte composition, voltage application, and annealing conditions that enhance crystallization and optimize electrical properties. As a result, the invention is not merely an adaptation of existing techniques but represents a novel methodological approach that leads to the realization of superior memristive devices.

The utility of this invention is profound, as it addresses significant barriers in the current technology landscape of memristors. The anodization process provides a reliable and efficient method to fabricate high-purity memristive materials that are essential for non-volatile memory and neuromorphic computing applications.

Thus the present invention addresses the shortcomings of the existing state of the art by introducing a cost-effective and scalable anodization process for synthesizing high-purity anodic molybdenum trioxide (α-MoO3) as a memristive material. This straightforward method permits the formation of uniform oxide layers without the need for complex equipment or highly controlled environments, significantly reducing production costs and enhancing accessibility for researchers and manufacturers alike. The anodization process enables easy optimization of fabrication parameters, resulting in excellent quality and consistency of the oxide layer. Importantly, the anodized α-MoO3 demonstrates superior electrical performance, characterized by improved resistive switching properties, retention, and endurance metrics. By providing a more efficient pathway to create high-purity oxide layers, my invention not only overcomes the limitations imposed by existing synthesis techniques but also advances the potential for broader applications in next-generation memristive devices.

In one of the preferred embodiment, the present invention shall discloses a method for fabricating a memristive device exhibiting improved switching speed and lower power consumption compared to conventional metal oxide-based memristors, thereby providing enhanced performance in electronic memory and synaptic emulation applications and making suitable for integration into existing electronic circuitry without substantial modifications. The method of the present invention comprises of following steps;

a. providing a molybdenum substrate and polishing with grit ranges from 100 to 2000 followed by cleaning with a soap solution, acetone, ethanol, and distilled water in an ultrasonic bath for 10 minutes each, followed by air drying to form molybdenum foil to functions as a bottom electrode;
b. performing a potentiostatic anodization of the molybdenum foil employing two-electrode configuration with the molybdenum foil serving as the working electrode (anode) and Platinum (Pt) mesh as counter electrode at a distance of 2.5 cm in 0.1M NH4F in a 5%/95% vol/vol water-ethylene glycol solution as electrolyte and applying a constant voltage of 40V for 1 hour at a stable anodization temperature of 23 °C (±1 °C) to obtain anodized sample of anodic α MoO₃ layer on molybdenum foil;
c. thermally annealing the anodized α MoO₃ layer at a temperature between 450 °C and 550 °C for 2 hours with a heating rate of 5 °C/min in a muffle furnace to from an insulating layer of anodically formed molybdenum trioxide (α MoO₃) on Mo foil; and
d. depositing a metallic silver Ag top electrode onto the molybdenum trioxide (α MoO₃) on Mo foil by DC magnetron sputtering using an Ag metal target (99.9%) with working pressure of 7.3 mTorr in 10 sccm in high purity (99.99%) Argon (Ar) gas with deposition time of 9 min under room temperature to form memristive device.

In yet another preferred embodiment, the present invention shall discloses a memristive device exhibiting improved switching speed and lower power consumption compared to conventional metal oxide-based memristors, thereby providing enhanced performance in electronic memory and synaptic emulation applications and making suitable for integration into existing electronic circuitry without substantial modifications. The device of the present invention comprising:

a. a substrate comprising molybdenum (Mo) foil to functions as a bottom electrode;
b. an insulating layer of anodically formed molybdenum trioxide (α MoO₃) on the Mo foil, in which the said α MoO₃ is produced by a potentiostatic anodization process in a fluorine‐based organic electrolyte; and
c. a top electrode comprising metallic silver (Ag) deposited on the insulating layer.
As per the invention, in the memristive device, the potentiostatic anodization is conducted in an electrolyte comprising 0.1 M NH₄F in a water–ethylene glycol mixture in a volumetric ratio of 5:95, respectively, at a constant voltage of 40 V for a duration of 1 hour at a temperature of about 23 °C ±1 °C.

According to the invention, in the memristive device, the anodically formed α MoO₃ is initially amorphous and is thermally annealed at a temperature between 450 °C and 550 °C for 2 hours with a heating rate of 5 °C/min to achieve a crystalline (orthorhombic) structure.

In accordance with the invention, in the memristive device, the top electrode is formed by DC magnetron sputtering of Ag under a working pressure of approximately 7.3 mTorr in a high-purity Argon (Ar) atmosphere, using a deposition time of 9 minutes under room temperature to yield a uniform Ag thin film having a thickness of about 600 nm and an electrode cross-sectional area of 1.2 mm × 1.2 mm.
Working Example:
A method for fabricating a memristive device comprises of following steps;
a. providing a molybdenum substrate and polishing with grit ranges from 100 to 2000 followed by cleaning with a soap solution, acetone, ethanol, and distilled water in an ultrasonic bath for 10 minutes each, followed by air drying to form molybdenum foil to functions as a bottom electrode;
b. performing a potentiostatic anodization of the molybdenum foil employing two-electrode configuration with the molybdenum foil serving as the working electrode (anode) and Platinum (Pt) mesh as counter electrode at a distance of 2.5 cm in 0.1M NH4F in a 5%/95% vol/vol water-ethylene glycol solution as electrolyte and applying a constant voltage of 40V for 1 hour at a stable anodization temperature of 23 °C (±1 °C) to obtain anodized sample of anodic α MoO₃ layer on molybdenum foil;
c. thermally annealing the anodized α MoO₃ layer at a temperature between 450 °C and 550 °C for 2 hours with a heating rate of 5 °C/min in a muffle furnace to from an insulating layer of anodically formed molybdenum trioxide (α MoO₃) on Mo foil; and
d. depositing a metallic silver Ag top electrode onto the molybdenum trioxide (α MoO₃) on Mo foil by DC magnetron sputtering using an Ag metal target (99.9%) with working pressure of 7.3 mTorr in 10 sccm in high purity (99.99%) Argon (Ar) gas with deposition time of 9 min under room temperature to form memristive device.
Although the invention has now been described in terms of certain preferred embodiments and exemplified with respect thereto, one skilled in art can readily appreciate that various modifications, changes, omissions and substitutions may be made without departing from the scope thereof. It is intended therefore that the present invention be limited solely by the scope of the following claims.
, Claims:WE CLAIM:

1. A method for fabricating a memristive device exhibiting improved switching speed and lower power consumption compared to conventional metal oxide-based memristors, thereby providing enhanced performance in electronic memory and synaptic emulation applications and making suitable for integration into existing electronic circuitry without substantial modifications, the claimed method comprises of following steps;

a. providing a molybdenum substrate and polishing with grit ranges from 100 to 2000 followed by cleaning with a soap solution, acetone, ethanol, and distilled water in an ultrasonic bath for 10 minutes each, followed by air drying to form molybdenum foil to functions as a bottom electrode;
b. performing a potentiostatic anodization of the said molybdenum foil employing two-electrode configuration with the said molybdenum foil serving as the working electrode (anode) and Platinum (Pt) mesh as counter electrode at a distance of 2.5 cm in 0.1M NH4F in a 5%/95% vol/vol water-ethylene glycol solution as electrolyte and applying a constant voltage of 40V for 1 hour at a stable anodization temperature of 23 °C (±1 °C) to obtain anodized sample of anodic α MoO₃ layer on said molybdenum foil;
c. thermally annealing the said anodized α MoO₃ layer at a temperature between 450 °C and 550 °C for 2 hours with a heating rate of 5 °C/min in a muffle furnace to from an insulating layer of anodically formed molybdenum trioxide (α MoO₃) on Mo foil; and
d. depositing a metallic silver Ag top electrode onto the said molybdenum trioxide (α MoO₃) on Mo foil by DC magnetron sputtering using an Ag metal target (99.9%) with working pressure of 7.3 mTorr in 10 sccm in high purity (99.99%) Argon (Ar) gas with deposition time of 9 min under room temperature to form memristive device.

2. A memristive device exhibiting improved switching speed and lower power consumption compared to conventional metal oxide-based memristors, thereby providing enhanced performance in electronic memory and synaptic emulation applications and making suitable for integration into existing electronic circuitry without substantial modifications, the claimed device comprising:

a. a substrate comprising molybdenum (Mo) foil to functions as a bottom electrode;
b. an insulating layer of anodically formed molybdenum trioxide (α MoO₃) on the said Mo foil, wherein the said α MoO₃ is produced by a potentiostatic anodization process in a fluorine‐based organic electrolyte; and
c. a top electrode comprising metallic silver (Ag) deposited on the said insulating layer.

3. The memristive device as claimed in claim 1, wherein the said potentiostatic anodization is conducted in an electrolyte comprising 0.1 M NH₄F in a water–ethylene glycol mixture in a volumetric ratio of 5:95, respectively, at a constant voltage of 40 V for a duration of 1 hour at a temperature of about 23 °C ±1 °C.
4. The memristive device as claimed in claim 1, wherein the said anodically formed α MoO₃ is initially amorphous and is thermally annealed at a temperature between 450 °C and 550 °C for 2 hours with a heating rate of 5 °C/min to achieve a crystalline (orthorhombic) structure.

5. The memristive device as claimed in claim 1, wherein the top electrode is formed by DC magnetron sputtering of Ag under a working pressure of approximately 7.3 mTorr in a high-purity Argon (Ar) atmosphere, using a deposition time of 9 minutes under room temperature to yield a uniform Ag thin film having a thickness of about 600 nm and an electrode cross-sectional area of 1.2 mm × 1.2 mm.

Dated this 16th day of MAY 2025

For PONDICHERRY UNIVERSITY
By its Patent Agent

Dr.B.Deepa
IN/PA 1477