arXiv subjects

Shubham Kumar Parate

Publications and source records attributed to Shubham Kumar Parate.

9 recordsLinked to original sources

arXiv2026

Large Pyroelectric Enhancement in Freestanding Epitaxial BaTiO3 Membranes on Si

Ferroelectric membranes transferred onto arbitrary substrates provide reduced mechanical clamping at the interfaces that can diminish the effective polarization-rotation barrier offering a pathway to engineer larger electromechanical and thermally driven responses in oxide electronics. Here, we report integration of single crystalline thin film BaTiO3 (BTO) ferroelectric membrane on Si and demonstrate a 4x at 30C and 34x at 60C enhancement of pyroelectric coefficient compared to clamped films. The BTO membrane is grown epitaxially on a water-soluble Sr3Al2O6 sacrificial layer, released by selective dissolution, and transferred onto Si, yielding a strain-relaxed membrane with robust intrinsic polarization. Temperature dependent piezoresponse force microscopy (PFM) reveals pronounced thermally driven evolution of domain orientation, consistent with reduced barriers for dipolar modulation in the freestanding state. Variable-temperature Kelvin probe force microscopy (KPFM) quantifies an effective pyroelectric coefficient of ~75 uC/m^2K at 30C and 450 uC/m^2K at 60C with a detectivity of 40 m^2K^-1at room temperature. These results establish lead-free freestanding BTO membranes as a promising silicon-integrable platform for cryogen-free infrared detection and waste-heat energy management.

cond-mat.mtrl-sci↗

arXiv2025

A facile vector substrate platform via BaTiO3 membrane transfer enables high quality solution processed epitaxial PZT on silicon

The direct integration of high-performance ferroelectric oxides with silicon remains challenging due to lattice mismatch, thermal incompatibility, and the need for high-temperature epitaxial growth. Here, a hybrid integration approach is demonstrated in which crystalline BaTiO3 (BTO) membranes are first transferred onto Pt coated Si substrates and subsequently used as vector substrates (VS) for the growth of epitaxial (001) Pb(Zr0.52Ti0.48)O3 (PZT) thin films via chemical solution deposition (CSD). A KI and HCl based etchant enables rapid and complete dissolution of the SrVO3 sacrificial layer in about 30 minutes, reducing the release time from days to minutes compared with conventional water based approaches to dissolve AVO3 and AMoO3 (A is Ca, Sr, Ba). The BTO VS imposes dominant (00l) out of plane orientation and in plane cube on cube epitaxy in the overlying PZT. Devices exhibit remnant polarization 10 to 12 micro coulomb/cm2 and coercive field of 100 kV/cm, with stable switching to 10^8 cycles on the VS. From piezoelectric butterfly loops, we extract effective d33 of 70 pm/V for PZT on VS, and 54 pm/V for PZT grown on conventional Pt Si substrates. This approach demonstrates a scalable and cost effective route for integrating functional ferroelectric materials onto silicon and offers a promising platform for future CMOS compatible oxide electronics.

cond-mat.mtrl-sci↗

arXiv2025

Anion Doping Driven Non-Ferroelectric-to-Ferroelectric Phase Transition in Epitaxial Y:HfO2

Oxygen vacancies are often essential for stabilizing the orthorhombic ferroelectric phase in HfO2, with cationic doping widely employed to introduce such defects. In contrast, systematic studies on anionic doping to induce ferroelectricity remains largely in nascent stages. Here, using epitaxial Y:HfO2 films grown on ITO-buffered YSZ substrates that initially crystallize predominantly in the monoclinic non-polar phase, we demonstrate that post-deposition rapid thermal annealing in N2 atmosphere at 900 {\deg}C enables nitrogen incorporation without disrupting epitaxy. As the annealing duration increases from 10 s to 2 min, the monoclinic phase diminishes, accompanied by the emergence of robust ferroelectric hysteresis and a corresponding increase in the orthorhombic phase fraction. Combining independent spectroscopic and compositional analyses, we experimentally establish that nitrogen preferentially incorporates into pre-existing neutral oxygen-vacancy sites, converting them into charged oxygen vacancies that drive the transformation from the non-polar monoclinic phase to the ferroelectric orthorhombic phase. Our epitaxial model platform therefore reveals an anion-mediated defect-engineering pathway for controlling ferroelectricity in Y:HfO2, establishing nitrogen incorporation not merely as a chemical dopant, but as a route to fundamentally reconfigure the defect thermodynamics governing phase stability in fluorite ferroelectrics.

cond-mat.mtrl-sci↗

arXiv2024

Epitaxial growth and stabilization of perovskite phase EuNiO3 thin films through RF sputtering

Phase change materials (PCMs) that exhibit volatile resistive switching are promising for emulating neuronal oscillators. Charge transfer insulators, such as ReNiO3 (where Re represents rare earth metals like Pr, Nd, Sm, Eu...), form a family of PCMs with tunable metal-insulator transition (MIT) temperatures across a broad range. Notably, MIT can be adjusted via chemical doping or strain engineering. EuNiO3, in particular, is an attractive choice for oscillator devices given its bulk transition temperature (TMI) of approximately 190{\deg}C, which is well above room temperature, reducing crosstalk issues while remaining low enough to support energy-efficient applications. We demonstrate a method to stabilize high-quality epitaxial EuNiO3 thin films through scalable reactive RF sputtering and post-annealing, optimizing oxygen partial pressures and annealing temperatures across two substrates. Growth at low or zero oxygen partial pressures resulted in amorphous samples, while higher pressures improved crystallinity but led to the stabilization of Ruddlesden-Popper (RP) phases [An+1BnO3n+1] and associated faults. Post-annealing enhanced crystallinity in all samples, transforming RP phases and faults toward the perovskite phase. We conducted operando XRD and transport measurements on our films, finding the transition temperatures of perovskite phase samples grown on LAO and LSAT to be approximately 300{\deg}C and 250{\deg}C, respectively. We attribute the increase in TMI for LAO samples to in-plane compressive strain (-0.76%), which reduces the Ni-O-Ni bond angles in-plane. Similarly, LSAT samples experience in-plane tensile strain (2.1%), which decreases out-of-plane Ni-O-Ni bond angles, increasing TMI compared to bulk. However, this is counteracted by oxygen vacancies due to lowered formation energies. Films that stabilized in RP phases did not exhibit any transition.

cond-mat.mtrl-sci↗

arXiv2024

Free Standing Epitaxial Oxides Through Remote Epitaxy: The Role of the Evolving Graphene Microstructure

Remote epitaxy has garnered considerable attention as a promising method that facilitates the growth of thin films that replicate the crystallographic characteristics of a substrate by utilizing two-dimensional (2D) material interlayers like graphene. The resulting film can be exfoliated to form a freestanding membrane, and the substrate, if expensive, can be reused. However, atomically thin 2-D materials are susceptible to damage before and during film growth in the chamber, leading to a poor epitaxy. Oxide remote epitaxy using graphene, the most commonly available 2D material, is particularly challenging because the conventional conditions employed for the growth of epitaxial oxides also degrade graphene. In this study, we show for the first time that a direct correlation exists between the microstructure of graphene, its getting defective on exposure to the pulsed laser deposition plume, and the crystalline quality of the barium titanate film deposited on top. A controlled aperture method was used to reduce graphene damage. Even so, the degree of damage is more at the graphene grain boundaries than within the grains. Large grain-sized greater than 300 microns, graphene suffered less damage and yielded a film comparable to that grown directly on a strontium titanate substrate with a rocking curve half width of 0.6 degrees. Using large grain-sized bi-layer graphene, 4 mm x 5 mm oxide layers were successfully exfoliated and transferred onto SiOx-Si. These insights pave the way for the heterogeneous integration of functional oxides on foreign substrates, holding significant implications for commercializing perovskite oxides by integrating them with Si-CMOS and flexible electronics.

cond-mat.mtrl-sci↗

arXiv2024

Room temperature Mott transistor based on resistive switching in disordered V2O3 films grown on Si

Electric field-induced giant resistive switching triggered by insulator-to-metal transition (IMT) is one of the promising approaches for developing a new class of electronics often referred to as Mottronics. Achieving this resistive switching by minimal external field at room temperature is of paramount research and technological interest. Mott-IMT is often associated with structural modification, which is very important for optoelectronic and actuator applications. Here, we report a giant resistive switching of about 900 % at room temperature in disordered polycrystalline V2O3-Si thin film stabilized at the IMT phase boundary and associated structural transformation under a small electric field. The increase of electron population in the a1g band under the field is responsible for the Mott gap collapse that drives the structural transition. Furthermore, we also fabricated a room temperature Mott-FET with a channel ON/OFF resistive ratio of about 15. This study provides a fundamental mechanism of the Mott-IMT in V2O3 as well as its device applications.

cond-mat.mtrl-sci↗

arXiv2024

Heterogeneous integration of high endurance ferroelectric and piezoelectric epitaxial BaTiO$_3$ devices on Si

Integrating epitaxial BaTiO$_3$ (BTO) with Si is essential for leveraging its ferroelectric, piezoelectric, and nonlinear optical properties in microelectronics. Recently, heterogeneous integration approaches that involve growth of BTO on ideal substrates followed by transfer to a desired substrate show promise of achieving excellent device-quality films. However, beyond simple demonstrations of the existence of ferroelectricity, robust devices with high endurance were not yet demonstrated on Si using the latter approach. Here, using a novel two-step approach to synthesize epitaxial BTO using pulsed laser deposition (PLD) on water soluble Sr3Al2O7 (SAO) (on SrTiO$_3$ (STO) substrates), we demonstrate successful integration of high-quality BTO capacitors on Si, with Pr of 7 uC/cm2, Ec 150 kV/cm, ferroelectric and electromechanical endurance of greater than $10^6$ cycles. We further address the challenge of cracking and disintegration of thicker films by first transferring a large area (5 mm x 5 mm) of the templated layer of BTO (~30 nm thick) on the desired substrate, followed by the growth of high-quality BTO on this substrate, as revealed by HRXRD and HRSTEM measurements. These templated Si substrates offer a versatile platform for integrating any epitaxial complex oxides with diverse functionalities onto any inorganic substrate.

physics.app-ph↗

arXiv2024

Record cryogenic cooling in ferroelectric hafnia proximity induced via Mott transition

On-chip refrigeration at cryogenic temperatures is becoming an important requirement in the context of quantum technologies and nanoelectronics. Ferroic materials with enhanced electrocaloric effects at phase transitions are good material candidates for the same. By exploiting the Mott metal-insulator transition (MIT) of TiOx(Ny), the bottom electrode, we engineer a depolarization field controlled reversible polar to non-polar phase transition in thick La-doped hafnia (40 nm). This transition occurs between ~125 and 140 K and produces giant negative pyroelectric and electrocaloric effects. Refrigeration metrics were estimated between 120 to 200 K, with a peak refrigerant capacity of 25 kJ Kg-1 (2 kJ Kg-1), peak isothermal entropy {\Delta}S~ 8 kJ Kg-1 K-1 (0.5 kJ Kg-1 K-1) and adiabatic {\Delta}Tcooling ~ 106 K (11 K) at ~140 K and 5 MV cm-1 (0.5 MV cm-1, and these are the largest reported in any electrocaloric system. Our work fundamentally proposes design guidelines to induce significant solid-state refrigeration through proximity effects, even at cryogenic temperatures relevant to quantum technologies.

cond-mat.mtrl-sci↗

arXiv2023

Giant electromechanical response from defective non-ferroelectric epitaxial BaTiO3 integrated on Si 100

Lead free, silicon compatible materials showing large electromechanical responses comparable to, or better than conventional relaxor ferroelectrics, are desirable for various nanoelectromechanical devices and applications. Defect-engineered electrostriction has recently been gaining popularity to obtain enhanced electromechanical responses at sub 100 Hz frequencies. Here, we report record values of electrostrictive strain coefficients (M31) at frequencies as large as 5 kHz (1.04 x 10-14 m2 per V2 at 1 kHz, and 3.87 x 10-15 m2 per V2 at 5 kHz) using A-site and oxygen-deficient barium titanate thin-films, epitaxially integrated onto Si. The effect is robust and retained even after cycling the devices >5000 times. Our perovskite films are non-ferroelectric, exhibit a different symmetry compared to stoichiometric BaTiO3 and are characterized by twin boundaries and nano polar-like regions. We show that the dielectric relaxation arising from the defect-induced features correlates very well with the observed giant electrostrictive response. These films show large coefficient of thermal expansion (2.36 x 10-5/K), which along with the giant M31 implies a considerable increase in the lattice anharmonicity induced by the defects. Our work provides a crucial step forward towards formulating guidelines to engineer large electromechanical responses even at higher frequencies in lead-free thin films.

cond-mat.mtrl-sci↗