Semiconductor Physics Lab
Research Field
By training, I am a semiconductor physicist. I study the physical properties of semiconductors, graphene, and two-dimensional materials.
For the past twenty-six years, I have been working to understand the electrical properties of devices and
nanostructures such as the two-dimensional electron gas (2DEG), quantum wires and quantum dots. The 2DEG
is a layer of electrons confined in a region as thin as 10 nm. Quantum wires are extremely small semiconductor
devices, 100 times narrower than a human hair, and their typical lengths are thousandth of a millimetre. The
size of a typical quantum dot is comparable to that of an influenza virus. My work on these ultra-small devices
of reduced dimensionality has led to observations of new and exciting physical phenomena, thereby
significantly advancing physics. In addition, some of my work may find potential applications in magnetic-
sensing, optical valve, optoelectronics, an electronic tongue for tea, and even sensing total mercury in blood.
Therefore my work is not only of fundamental importance but also has its application for economic and social
benefit. I have published more than 280 papers in primary peer reviewed journals and my h-index is 35. My
work was listed in IOP Select twice, highlighted by nanotechweb.org, and was amongst the most downloaded
in Japanese Journal of Applied Physics and Nanoscale, and high-accessed in Nanoscale Research Letters (four
times). According to the Institute for Scientific Information, my work has been cited over 5389 times which is
compelling evidence of its impact on the field.
1. Random lasing and high photo-responsivity in 2D perovskites
We studied millimeter-sized single-crystalline perovskite microrods and have observed low-threshold random lasing behaviour. The single-crystalline two-dimensional (2D) hybrid perovskite random laser achieved a narrow linewidth (»0.1 nm) with a low threshold (»0.5 μJ/cm2) and a high-quality factor Q (»5350). Our 2D hybrid microrod laser shows stable lasing emission with no measurable degradation after at least 2 h under continuous illumination, which substantially proves the stability of 2D perovskites. Our results demonstrate the promise of 2D organic–inorganic microrod-shaped perovskites and may provide an important step toward the realization of high-performance optoelectronic devices [Work 1]. We prepared a photoconductive device fabricated using (N-MPDA)[PbBr4] single crystal which exhibits an excellent photoresponsivity (≈124 A/W at 405 nm) that is ≈4 orders of magnitudes higher than that of monovalent organic spacer-assisted 2D perovskites, such as (BA)2PbBr4 and (PEA)2PbBr4, and large specific detectivity (≈1012 Jones). As an optical gain media, the (N-MPDA)[PbBr4] single crystal exhibits a low threshold random lasing (≈6.5 mJ/cm2) with an angular-dependent narrow linewidth (≈0.1 nm) and Q ≈ 2673 [Work 2].
2. High-performance photodetectors with upconversion/Au/Prussian-Blue (PB) nanocomposites
We demonstrate a one-pot hydrothermal method for novel in situ preparation of upconversion nanoparticles (UCNP)@Au composites using a binary functional ethylenediaminetetraacetic salt, which is employed as a surfactant and reducing agent [Work 3]. The composites are electrostatically conjugated with metal-coordinated PB to yield UCNP@Au+PB nanocomposites (NCs), which demonstrate 21-fold upconversion emission quenching by fluorescence resonance energy transfer compared to UCNPs. Additionally, the PB, UCNP@Au, and NCs demonstrate a synergistically reduced trap (α ≈ 0.85) and enhance ultrasensitive broadband (432–980 nm) photodetection. The NCs-based gate-free epitaxial graphene device demonstrates excellent high photoresponsivity (5.9 × 105 A/W), detectivity (2.17 × 1014 cm ÖHz/W), and normalized gain (2.06 × 10−4 m2 /V) at 318 nW/cm2 (532 nm) and a bias voltage of 1 V.
3. Quantum phase transitions in superconductors and semiconductors
We show that substrate and interface effects play a key role in enhanced superconductivity in ultraclean, wafer-scale MBE-grown Al nanofilms [Work 4]. We are the first to observe a direct transition from an insulating state to a high Landau level filling factor (nu=6) quantum Hall state in graphene [5] and we show that in graphene on SiC the inelastic scattering exponent p is shifted from 1 at low magnetic fields to 2 near the quantum Hall regime [Work 6].
References
1. Pradip Kumar Roy, Rajesh Kumar Ulaganathan, Chinnambedu Murugesan Raghavan, Swapnil Milind Mhatre, Hung-I Lin, Wei-Liang Chen, Yu-Ming Chang, Alex Rozhin, Yun-Tzu Hsu, Yang-Fang Chen, Raman Sankar*, Fang-Cheng Chou*, and Chi-Te Liang*, Unprecedented random lasing in 2D organolead halide single-crystalline perovskite microrods (2020), Nanoscale 12, 18629
2. Rajesh Kumar Ulaganathan, Pradip Kumar Roy, Swapnil Milind Mhatre, Raghavan Chinnambedu Murugesan, Wei-Liang Chen, Man-Hong Lai, Ambika Subramanian, Chang-Yu Lin, Yu-Ming Chang, Stela Canulescu, Alex Rozhin, Chi-Te Liang*, and Raman Sankar*, High-performance photodetector and angular-dependent random lasing from long-chain organic diammonium sandwiched 2D hybrid perovskite non-linear optical single crystal (2023), Adv. Funct. Mater. 33, 22140
3. Akash Gupta, Dinesh Kumar Patel, Song Yeul Lee, Albert F. Rigosi, Randolph E. Elmquist, Venkata N. K. B. Adusumalli, Chi-Te Liang*, and Yong Il Park*, Record-high responsivity and high detectivity broadband photodetectors based on upconversion/gold/Prussian-blue nanocomposite (2022), Adv. Funct. Mater. 32, 2206496
4. Ching-Chen Yeh, Thi-Hien Do, Pin-Chi Liao, Chia-Hung Hsu, Yi-Hsin Tu, Hsin Lin, T.-R. Chang, Siang-Chi Wang, Yu-Yao Gao, Yu-Hsun Wu, Chu-Chun Wu, Yu An Lai, Ivar Martin, Sheng-Di Lin*, Christos Panagopoulos*, and Chi-Te Liang*, Doubling the superconducting transition temperature of ultraclean wafer-scale aluminum nanofilms (2023), Phys. Rev. Mater. 7, 114801.
5. Ching-Chen Yeh, Pin-Chi Liao*, Dinesh K. Patel, Wei-Chen Lin, Siang-Chi Wang, Albert F. Rigosi, Randolph E. Elmquist, Chi-Te Liang*, Direct insulator-relativistic quantum Hall transition in graphene (2023), Phys. Rev. B 108, 205304.
6. C.-C. Yeh, P.-C. Liao, Y. Yang, W.-C. Lin, A. R. Panna, A. F. Rigosi, R. E. Elmquist, and C.-T. Liang*, Conformity experiment on inelastic scattering exponent of electrons in two dimensions (2024), Phys. Rev. Lett. 133, 096302.
‧ Elected Fellow of the Physical Society of Taiwan (TPS) (2024)
‧ Elected Fellow of the Institute of Physics (FInstP), United Kingdom (2014)
‧ Outstanding teaching awards, NTU (2010, 2020, 2021, 2022, 2023, and 2024)
‧ Chinese Journal of Physics (CJP) Excellent Paper Prize (2011)
‧ Supervisor of College students participating in special research project of creative award provided by the
NSC (2009)
‧ Lam Research Award, Taiwan (2004, 2011 and 2014)
‧ A merit winner of the “Young Science Writer” competition by the Daily Telegraph and British Association,
UK (1993)
‧ Overseas Research Studentship (ORS) provided by the Committee of Vice Chancellors and Principals
(CVCP), UK (1993-1995)
Bachelor of Science, Department of Physics, National Taiwan University, Taiwan (1990)
Doctor of Philosophy, Cavendish Laboratory, University of Cambridge, United Kingdom (1996)
2 Vacancies
Job Description
Research Topics
Semiconductor science and materials, Nanomaterials for energy and bioapplications, Electronics and optoelectronics, Catalysis.
Preferred Intern Education Level
Mostly Master or PhD students, particularly for students with a master degree and looking for PhD or postdoc opportunity
Skill sets or Qualities
Excellent scientific reasoning and writing ability, outstanding personal academic record in national ranking