InN 나노와이어 기반 자가구동 모션센서 제작 및 휴먼-머신 인터페이스 응용 연구 = Fabrication of self-powered piezoelectric motion sensor based on InN nanowires and their application to human-machine interface

다국어 초록 (Multilingual Abstract)

In this thesis, we discussed device performances of self-powered piezoelectric motion sensors (PMSs) fabricated with spatially aligned InN nanowires (NWs) as a response medium and their application example to human-machine interface system. The InN NWs were grown on a Si(111) substrate using a new growth method, In pre-deposition method, with a plasma-assisted molecular-beam epitaxy. The structural and optical characterization indicates the formation of high-crystalline InN NWs, in which stacking faults commonly present in Si-based III-V semiconductor NWs are rarely observed.
Self-powered PMSs with double-electrode configuration were fabricated with spatially aligned InN NWs by applying a magnetic field. Specifically, applying a magnetic field of 50 G ensured that the InN NWs were fully aligned along the field direction. The output voltage of the PMS with the InN NWs aligned along the bending direction was measured to be 3.05 V, which is 2.44 times higher than that (1.25 V) of the device with randomly distributed InN NWs. This result is much higher than those of the previous reports. Attachment of the self-powered PMSs to human joints such as the finger, wrist, elbow, and knee revealed that these motion sensors are highly effective, thereby indicating the possibility of detecting the various motions of the human body.
Compared to motion sensors with a double-electrode configuration, a single-electrode PMS offers notable advantages, including structural simplicity, elimination of the shielding effect of the top electrode, and a reduced risk of failure resulting from short-circuiting. Self-powered PMSs with single-electrode configuration were fabricated with spatially aligned InN NWs and graphene as the response medium and channel of carrier movement, respectively. Systematic analysis of the self-powered PMSs by varying the degree of strain, relative humidity, number of bending cycles, and operational time (up to 30 days) indicates that the device performance is sufficient for practical application. A PMS module composed of 14 chips attached to the finger joints of a left hand was able to successfully distinguish hand-gestures corresponding to the volume of an object (softball, baseball, and golf ball). Thess results demonstrate that single-electrode PMSs with InN NWs could contribute to realizing sophisticated human-machine interface technology.

목차 (Table of Contents)

• - CONTENTS -
• Contents i
• Abstract (English) iii
• List of figures vi
• List of tables xi
• Chapter 1. Introduction 1
• 1.1. Formation of high-crystalline III-nitride nanowires (NWs) 1
• 1.2. Fabrication of piezoelectric motion sensors (PMSs) and their application to human-machine interface 7
• References 13
• Chapter 2. Theoretical backgrounds 17
• 2.1. Formation of III-nitride NWs 17
• 2.1.1. Conventional growth modes for III-nitride NWs 17
• 2.1.2. Self-induced growth mode for III-nitride NWs 18
• 2.2. Piezoelectric effect in InN NWs 20
• References 24
• Chapter 3. Experimental details 26
• 3.1. Plasma-assisted (PA) molecular-beam epitaxy (MBE) 26
• 3.2. Formation method for high-crystalline III-nitride NWs on Si(111) 28
• 3.3. Scanning electron microscope (SEM) 30
• 3.4. X-ray diffraction (XRD) 32
• 3.5. Transmission electron microscope (TEM) 34
• 3.6. Photoluminescence (PL) spectroscopy 36
• 3.7. Raman spectroscopy 38
• 3.8. Source meter 40
• 3.9. Piezoresponse force microscopy (PFM) 42
• References 44
• Chapter 4. Results and discussion 45
• 4.1. Formation of high-crystalline InN NWs 45
• 4.2. Spatial alignment of InN NWs 65
• 4.3. Fabrication of self-powered PMS with double-electrode configuration using spatially aligned InN NWs 72
• 4.4. Improvement of self-powered PMS with InN NWs using single-electrode configuration 89
• 4.5. Hand-gesture recognition using single-electrode PMS 110
• References 119
• Chapter 5. Conclusion 123
• Abstract (Korean) 126
• Acknowledgements 129