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Fabrication and optimization of magnetoresistive thin film structure for improved spintronic sensors

Title
Fabrication and optimization of magnetoresistive thin film structure for improved spintronic sensors
Translated Title
향상된 스핀 트로닉스 센서를위한 자기 저항 박막 구조 제작 및 최적화
Authors
Amir Aly Ibrahim Elzawawy
DGIST Authors
Elzawawy, Amir Aly Ibrahim; Lee, Hyeon-JunKim, CheolGi
Advisor(s)
김철기
Co-Advisor(s)
Hyeon-Jun Lee
Issue Date
2019
Available Date
2019-08-23
Degree Date
2019-08
Type
Thesis
Description
Sensors
Table Of Contents
Abstract -------------------------------------------------------------------------------------------------- i Acknowledgment -------------------------------------------------------------------------------------- iii Table of contents ---------------------------------------------------------------------------------------- v List of figures ------------------------------------------------------------------------------------------ viii List of tables --------------------------------------------------------------------------------------------- x List of abbreviations ----------------------------------------------------------------------------------- xi Outline of the thesis ----------------------------------------------------------------------------------- xii I. Introduction ------------------------------------------------------------------------------------------ 1 1.1 Exchange bias in FM/AFM bilayers ------------------------------------------------------------- 1 1.1.1 FM layer material and thickness effect ---------------------------------------------------- 3 1.1.2 AFM layer material and thickness effect -------------------------------------------------- 3 1.1.3 Interface roughness effect ------------------------------------------------------------------- 4 1.1.4 Seed layer effect ------------------------------------------------------------------------------ 4 1.1.5 Capping layer effect -------------------------------------------------------------------------- 5 1.2 Exchange bias in FM/NM/AFM trilayers: spacer layer material and thickness effect ---- 5 1.3 Magnetoresistance and planar Hall effect ------------------------------------------------------- 5 1.4 Planar Hall effect sensors: operating field range, output voltage, and shunt current ------ 6 1.4.1 PHE sensors without exchange bias in NiFe single layer ------------------------------- 7 1.4.2 PHE sensors with exchange bias in NiFe/IrMn bilayer --------------------------------- 9 1.4.3 PHE sensors with exchange bias in NiFe/Spacer/IrMn trilayer ------------------------ 13 1.5 Sensitivity of planar Hall effect sensors --------------------------------------------------------- 16 1.6 Noise in magnetoresistance sensors -------------------------------------------------------------- 16 1.6.1 Barkhausen noise ----------------------------------------------------------------------------- 16 1.6.2 Thermal noise --------------------------------------------------------------------------------- 17 1.6.3 1/f noise ---------------------------------------------------------------------------------------- 17 1.6.4 Reduction of noise by optimization of layer composition and sensors shape -------- 17 II. Experimental techniques ------------------------------------------------------------------------- 19 2.1 Materials --------------------------------------------------------------------------------------------- 19 2.2 Samples fabrication -------------------------------------------------------------------------------- 19 2.2.1 Photolithography method -------------------------------------------------------------------- 19 2.2.1.1 Optimization of UV exposure time and developing time ------------------------- 23 2.2.2 Lift off method -------------------------------------------------------------------------------- 24 2.2.3 DC magnetron sputtering system ----------------------------------------------------------- 24 2.2.3.1 Characterization of deposition rate --------------------------------------------------- 24 2.2.3.2 Adjustment of sample location on the sample holder with the built in magnet - 25 2.2.4 Sensor deposition ----------------------------------------------------------------------------- 28 2.2.5 Electrode deposition -------------------------------------------------------------------------- 28 2.3 Samples characterization -------------------------------------------------------------------------- 29 2.3.1 Planar Hall effect measurements ------------------------------------------------------------ 29 2.3.2 Vibrating sample magnetometry (VSM) --------------------------------------------------- 30 2.3.3 Noise measurements ------------------------------------------------------------------------- 30 2.3.4 Atomic force microscopy (AFM) ---------------------------------------------------------- 31 2.3.5 High resolution transmission electron microscopy (HR-TEM) ------------------------ 32 2.3.6 X-ray diffraction spectroscopy (XRD) ---------------------------------------------------- 32 III. Tailoring of exchange bias by material and thickness variation of seed layer ------- 33 3.1 Hybrid seed layer material and thickness effects on crystallinity and growth direction of FM and AFM layers for NiFe/IrMn bilayer---------------------------------------------------------- 33 3.2 Ta/Cu and Ta/Au hybrid seed layer effects on the exchange bias with NiFe/IrMn bilayer --------------------------------------------------------------------------------------------------------------- 39 3.3 NiFeCr seed layer effects on the exchange bias field in NiFe/Au/IrMn trilayer ----------- 40 IV. Interlayer material effects for the multilayer structures --------------------------------- 44 4.1 Effect of the NM interlayer material on the parameters of magnetic hysteresis loop for NiFe/NM/NiFe trilayers ------------------------------------------------------------------------------- 44 4.2 NiFeCr as a spacer layer in NiFe/Spacer/IrMn trilayer --------------------------------------- 48 V. Capping layer material effects on the exchange bias for multilayer structures ------- 49 5.1 NiFeCr capping layer effects on the exchange bias field in NiFe/Au/IrMn trilayer ------- 49 VI. Effect of active layers on sensor’s output voltage, operating field range, sensitivity and noise in multilayer structures ----------------------------------------------------------------- 51 6.1 NiFeCr as an active FM layer and AFM in comparison with NiFe/IrMn bilayer structure --------------------------------------------------------------------------------------------------------------- 51 6.2 Magnetic field sensitivity of PHE sensors, based on NiFe/Au/IrMn trilayer junctions, grown with Ta and NiFeCr seed and capping layers -------------------------------------------------------- 52 6.3 Optimization of sensitivity by material and thickness variation of FM layer in FM/IrMn bilayer ---------------------------------------------------------------------------------------------------- 57 6.4 Untethered operating field range adjustment by interdependent variation of non-magnetic spacer and capping layers thicknesses ---------------------------------------------------------------- 67 6.5 Magnetoresistance response in sweeping magnetic field for NiFe/NM/NiFe trilayer ----- 73 6.6 Uncorrelated responses of PHE and AMR to Barkhausen jumps in sweeping magnetic field for NiFe/NM/NiFe trialyer ----------------------------------------------------------------------------- 77 6.7 The planar Hall voltage noise in stationery magnetic field for NiFe/NM/NiFe trialyer --- 82 Conclusions and perspectives ----------------------------------------------------------------------- 87 List of publications ------------------------------------------------------------------------------------ 93 List of conferences ------------------------------------------------------------------------------------- 94 Summer school and internship ---------------------------------------------------------------------- 97 References ---------------------------------------------------------------------------------------------- 98
URI
http://dgist.dcollection.net/common/orgView/200000217242
http://hdl.handle.net/20.500.11750/10459
DOI
10.22677/thesis.200000217242
Degree
Doctor
Department
Department of Emerging Materials Science
University
DGIST
Related Researcher
  • Author Kim, CheolGi Lab for NanoBio-MatErials & SpinTronics(nBEST)
  • Research Interests Magnetic Materials and Spintronics; Converging Technology of Nanomaterials and Biomaterials; Bio-NEMS;MEMS
Files:
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Collection:
Department of Emerging Materials ScienceThesesPh.D.


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