Probing of Spin-dependent properties of Topological Insulator(TI)/Co Interface and Investigation on ITO/Co/TI/Co/Au vertical Spin-Valve Device Ref.No.SSTCRC2590

Putdate:2025-06-04

Probing of Spin-dependent properties of Topological Insulator(TI)/Co Interface and Investigation on ITO/Co/TI/Co/Au vertical Spin-Valve Device Ref.No.SSTCRC2590


1. Introduction

Topological insulators (TIs) emerge out as promising and potential candidates for Spintronic devices, in particular for applications where all-electrical spin controlling is required. Spin dynamics of this novel class of material, persisting even up to room temperature, suggests great potential for TIs in spintronic devices.

Definition of Problems: Topological Insulators (TIs) are known to have the capability of generation of spin-polarized currents. However, very little is known about the spin injection/extraction into/out of them. Furthermore, the way of interaction and exploitation of the TI surface state still remains elusive. Thus, the knowledge on spin pumping and hence investigation on spin transfer dynamics at the TI/ferromagnet interface is essential in a spin-valve like structure.

Motivation: As topological surface states in TIs offer exciting prospects for dissipationless spin transport, we aim to demonstrate spin pumping from a ferromagnetic layer through the TI layer and into the ferromagnetic spin sink. In this direction in my proposed work, we aim and plan to fabricate (a) Vertical spin valve structures, comprising the 3D TIs, i.e., Bi2Te3 or Bi2Se3 as channel with Co as ferromagnetic injector/detector electrodes and (b) TI/ferromagnet interface by electron beam evaporation method on ITO substrate.


2. Objectives

1. Designing and Fabrication of spin valve structures, comprising 3D TIs, i.e.,ITO/Co/TI/Co/Au and TI/ferromagnet interface [where TI = Bi2Te3 or Bi2Se3].[Initially, the device junction area is ≈ 2 × 2 mm2 with subsequent junction size of 25 x 25 μm2 or less. For smaller junction size, we would like to do the collaboration.]

2. Confirmation of the topological nature of Bi2Se3 and Bi2Te3 in spin-valve device and interface.

3. Demonstration of full characterization of the said spin valves and interfaces.

4. Fabrication of a 4 x 4 or larger array design on a fanout board with at least 16 device performance histograms to illustrate uniformity and performance equivalent to single devices.

5. Investigation of Spin-Valve properties.

6. Investigation of spin-dependent properties and spin transfer dynamics of TI/Co Spinterface.


3. Research Progress

Preliminary Results : In our research group, we have already initiated experimental work on spin valve structures, employing 3D TIs as spacer layer, i.e.,ITO/Co/TI/Co/Au and TI/ferromagnet interface [where TI = Bi2Te3 or Bi2Se3], using instruments available at our Laboratory in the Department of Physics, Kazi Nazrul University, Asansol, W. B., India.


The brief experimental details of this work are given below : Fabrication of ITO/Co/TI/Co/Au and TI/ferromagnet interface have been carried out employing a customized multi-crucible thin film deposition unit (base pressure ~ 5 × 10-7 mbar), consisting of both electron beam evaporation and thermal evaporation system. Characterizations including FE-SEM (ZEISS SIGMA), AFM (Bruker di INNOVA), and UV-vis spectroscopy, with additional measurements (EDAX, XRD) were performed. DC transport study has been performed with a Keysight (B2902A) source meter available at our Laboratory (Kazi Nazrul University). Spin-valve Magnetoresistance has been monitored in our device structure.

Some important results obtained in our fabricated spin-valve heterostructures are given below :

* Bias voltage mediated transition from Bulk Non-Conducting to Surface dominated Conducting State.

* Positive photogeneration under IR illumination and Negative photogeneration under 660 nm red light illumination.

* Time varying AC electric field driven ON and OFF states and AC coupled activated IR response.


Work Remaining :

Regarding Designing and Fabrication - Initially, the device junction area of spin valve structures and interfaces is ≈ 2 × 2 mm2 with subsequent junction size of 25 x 25 μm2 or less. For smaller junction size, we would like to do the collaboration.Considering our Objectives described above, point number 2, some characterizations related to point no. 3, point no. 4 and 6 remain to be completed.


4. Cooperation Required

(i) Funding for Research : We are looking for International Funding for this research with International Collaboration.

(ii) Cooperation of other research teams : We would like to do collaboration for high end experimental facilities, such as device fabrication of spin valve structures and interfaces having junction size of 25 x 25 μm2 or less (we have already done the same for 2 × 2 mm)2, investigation of spin dynamics at interface, high-end characterizationsfor confirmation of the topological nature of Bi2Se3 and Bi2Te3 in spin-valve device and interface.


5. Benefits and Outputs

-Research Work carried out on this project idea seems to suggest that incorporation of TI would be promising in IR detection technology and next generation high performance Focal Plane Array.

-Expected Outcomes

Device Performance : * High-efficiency broadband photodetection across visible and IR regions. * Significant magnetoresistance, spin polarization and optically modulated spin valve response.

Scientific Contributions : * Insights into spin-photon interactions in ferromagnetic /TI interface. * Novel device architecture for multifunctional applications.

Technological Impact : * Prototype demonstration of a compact, topological insulator based multifunctional device. * Potential integration into quantum computing and optoelectronic systems.

-The experimental results of this project, which are relevant to the technological development of electrically controlled modern spin-based devices, are aimed to be published in high impact international journals. The findings from this proposed project, which have strong commercial application aspects, will be patented.



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