File(s) under permanent embargo

Reason: Restricted by author. A copy can be supplied under Section 51(2) of the Australian Copyright Act 1968 by submitting a document delivery request through your library or by emailing

Preparation of atomic-layer transition metal chalcogenides with application in opto-electronic devices

posted on 27.02.2017, 00:13 by Xu, Zaiquan
Graphene like two-dimensional materials are important elements of potential optoelectronics applications due to their exceptional electronic and optical properties. The preparation and processing of these materials towards the realization of opto-electronic devices has been one of the main motivations for the recent development of photonics and optoelectronics. My Ph.D projects involves with three aspects: 1. Preparations of atomic-layer transition metal dichalcogenides (TMDs), e.g. MoS₂ , WS₂ and WSe₂ with chemical vapour depositions. In this part, we present the synthesis of large size (>100 μm) single crystals of atomically thin tungsten disulfide (WS₂ ), a member of TMDs family, on sapphire substrate. More importantly, we demonstrate a polystyrene (PS) mediated delamination process via capillary force in water which allows recyclable use of the growth substrates; 2. Fabrication of TMDs based photodetectors and study the performance and mechanisms with spatial photocurrent mapping. We developed an efficient photodetector with extremely large photo-responsive active area based on a lateral p-n junction of monolayer-bilayer WSe₂ . The junction is produced by partially peeling off the upper layer of a bilayer WSe₂ crystal grown by atmospheric pressure chemical vapour deposition. Kelvin probe force microscope and photocurrent mapping were used to understand the performance and the mechanism; 3. Atomic layered thin TMDs based flat lenses: fabrication and imaging. An ultrathin flat lens with a thickness of 7 Å, which corresponds to the fundamental physical limit of material thickness, is fabricated on a large monolayer WSe2 single crystals with direct femtosecond laser writing. We apply the material with ultra-high refractive index to achieve three-dimensional (3D) focusing with almost diffraction-limited resolution by effective modulation of the amplitude of the incident light.


Campus location


Principal supervisor

Qiaoliang Bao

Year of Award


Department, School or Centre

Materials Science and Engineering


Doctor of Philosophy

Degree Type



Faculty of Engineering