Title

Enhanced Electrical Performance of SnS₂ Field-Effect Transistors through Phase-Engineered HfO₂

DGIST Authors

Chong-Myeong Song ; Hyuk-Jun Kwon ; Shinbuhm Lee

Advisor

권혁준

Co-Advisor(s)

Shinbuhm Lee

Issued Date

2026

Awarded Date

2026-02-01

Type

Thesis

Description

2D Semiconductors, SnS₂, Y:HfO₂, La:HfO₂, HZO, FeFET, Negative Capacitance, Bi contact, MIGS suppression, Neuromorphic, Low-power switching, CMOS compatibility

Table Of Contents

Ⅰ. Introduction 1
1.1 Beyond Moore's Law and Power Scaling Challenges in Computing 1
1.2 Two-Dimensional (2D) Materials for Next-Generation Transistors 3
1.3 Key Bottlenecks in 2D Transistor Technology 7
1.4 Dissertation Outline 9

Ⅱ. Theoretical Background 10
2.1 Isolated band 2D SnS₂ 10
2.2 Fermi-Level Pinning at Metal/2D Semiconductor Interfaces 16
2.3 Phase Engineering of HfO₂ Thin film for Advanced Transistor Applications 19
2.3.1 Crystalline Phases and Doping effects 21
2.3.2 Ferroelectricity in HfO₂ Thin Film 23
2.3.3 Methods for inducing ferroelectricity in HfO₂ 24
2.3.4 Atomic Layer Deposition (ALD) 25
2.3.5 Chemical Solution Deposition (CSD) 26
2.3.6 Thermal Annealing 28
2.3.7 Analysis of Ferroelectric HfO₂ Film 29
2.3.8 Negative Capacitance(NC) Effect 32
2.3.9 Negative Capacitance Field Effect Transistor (NCFET) 34

Ⅲ. High-Performance SnS₂ Field-Effect Transistors with semimetal Bi Contact and high-k Y:HfO₂ 36
3.1 Introduction 36
3.2 Experimental Section 37
3.2.1 Fabrication of Y:HfO₂ thin film 37
3.2.2 Fabrication of Bi-SnS₂ FET on Y:HfO₂ film 37
3.2.3 Optical and Electrical Characterization 38
3.2.4 DOS Calculation 38
3.2.5 Contact resistance extract of Bi-SnS₂ FET (Y-function Method) 39
3.3 Results and Discussion 39
3.3.1 Characterization of Y:HfO₂ thin film 39
3.3.2 Semimetal Bismuth-SnS₂ Contact 44
3.3.3 I-V Characteristics of Bi-SnS₂ on Y:HfO₂ film 48
3.4 Conclusion 49

Ⅳ. Sub-thermionic and Hysteresis-free SnS₂ Negative Capacitance Field-Effect Transistors with La:HfO₂ 51
4.1 Introduction 51
4.2 Experimental Section 52
4.2.1 Fabrication of SnS₂ NCFETs 52
4.2.2 Characterization 53
4.2.3 Computational Methods 53
4.3 Results and Discussion 53
4.3.1 Band Structure of MoS₂ vs SnS₂ 53
4.3.2 La:HfO₂/HfO₂ Negative Capacitance (NC) 56
4.3.3 I-V characteristics of SnS₂ NCFET 61
4.4 Conclusion 66

V. Ferroelectric SnS₂ Analog Synaptic Transistors for Neuromorphic Computing with Zr:HfO₂ 67
5.1 Introduction 67
5.2 Experimental Section 69
5.2.1 Device fabrication of SnS₂ FET 69
5.2.2 Characterization of SnS₂ FET 69
5.3 Results and Discussion 70
5.3.1 Analysis and Evaluation of ferroelectric HZO film 70
5.3.2 The hysteresis window of the SnS₂/HZO synaptic transistor 72
5.3.3 The synaptic characteristics of the SnS₂/HZO transistor 74
5.4 Conclusion 79

Ⅵ. Summary and Future Works 80
6.1 Summary 80
6.2 Future works 81

References 85

URI

https://scholar.dgist.ac.kr/handle/20.500.11750/59632
http://dgist.dcollection.net/common/orgView/200000946680

DOI

10.22677/THESIS.200000946680

Degree

Doctor

Department

Department of Electrical Engineering and Computer Science

Publisher

DGIST

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