Crystallization Kinetics for Homo- and Hetero-genous Thin Films of Tungsten Selenide
Single to few-layered Group-VI semiconducting transition metal dichalcogenides (TMD) are new materials that exhibit versatile physical properties, such as sizable direct band gaps, that promise new potential for many electronic and optoelectronic devices. A prototypical TMD, Tungsten Selenide (WSe2) exhibits captivating properties such as room temperature photoluminescence temperature. However, the integration of WSe2 and other TMDs into devices is currently limited due to the inaccessibility of scalable techniques to fabricate high quality large area thin films. This impediment can be resolved by understanding and optimizing the kinetics of film growth. Thus, our work encompasses innovative techniques to study the crystallization kinetics of thin amorphous homo- and hetero-genous films of WSe2. We begin by sputtering thin amorphous films of WSe2 on flexible and rigid substrates. We then crystallize the deposited films by supplying enough energy for crystallization via broadband radiation, nanoscale beams, and in situ Raman Spectroscopy. Magnetron sputtering is selected as the deposition technique due to the low temperatures involved, thus allowing deposition on polymer substrates. Furthermore, modulation of the energy flux during magnetron sputtering provides an opportunity to model homo or hetero crystallization by forbidding or permitting the presence pre-existing nuclei, respectively. Our employment of various crystallization techniques allows for methodical study of the influences of seeds on 2D nucleation and growth kinetics. Results show that homogenous crystallization has a lower nucleation due to the small seed size. Such finding is systematically explained by crystallization theories that relate the critical radius size of the seeded materials to energy barriers. The newly founded relationship between deposition parameters, activation barriers, and film quality of WSe2 is applicable to other TMDs. Thus, our work significantly contributes to the advancement TMDs and eases their incorporation in future electronic devices.
Primary Advisor's Department
Stander Symposium poster
"Crystallization Kinetics for Homo- and Hetero-genous Thin Films of Tungsten Selenide" (2019). Stander Symposium Posters. 1627.