Jonathan R. Chin

Advisor: Professor Lauren M. Garten

will defend a doctoral thesis entitled,

DEVELOPING THIN FILM DEPOSITION METHODS TO PROMOTE
ORIENTATION AND LAYERING IN TIN SELENIDE FOR PIEZOELECTRIC ANALYSIS

On

Tuesday, March 10, 2026
1:00 pm - 3:00 pm

Price Gilbert 4222
Georgia Tech Library Dissertation Defense Room
or virtually via Zoom:
Zoom link


Committee:
Professor Lauren M. Garten - School of Materials Science and Engineering (advisor)
Professor Juan-Pablo Correa-Baena - School of Materials Science and Engineering
Professor Mark Losego - School of Materials Science and Engineering
Professor Eric Vogel - School of Materials Science and Engineering
Professor Stephanie Law - Department of Materials Science and Engineering, The Pennvylsania State University

Abstract:

   The development of 2D piezoelectric materials is critical for the continued miniaturization of an array of electrical technologies, including sensors, actuators, energy harvesters, piezotronics, and more. 2D SnSe is projected to have a d11 coefficient of 250 pm/V, which is significantly greater than other lead-free piezoelectrics such as AlN (d11 ≈ 5 pm/V) and MoS2 (d11 ≈ 4 pm/V). However, SnSe should only exhibit an in-plane piezoelectric response for an odd number of layers near the monolayer limit. Therefore, a processing method with strict layer control down to the monolayer limit is needed for SnSe films to determine the piezoelectric coefficient and to incorporate this material into devices at scale.
   
   The work described in this dissertation demonstrates how to utilize molecular beam epitaxy (MBE) to synthesize stoichiometric SnSe thin films with layer control down to near-monolayer thicknesses (2-8 nm) with consistent crystallographic orientation control. We determined the mechanisms of stoichiometry control of SnSe using the self-limiting nature of selenium clustering for flux ratios up to 1.35:1 Se:Sn. We find that, in addition to the flux ratio, the flux timing (Se first or Sn first) impacts the in-plane film coverage with higher Se concentrations inducing lateral grain growth. We also demonstrate that the SnSe films are chemically inert, with a thin layer of SnO2 at the surface that does not propagate throughout the film thickness upon atmospheric exposure. After establishing the stoichiometry, orientation, and layer control, these SnSe films were processed into test devices via photolithography to evaluate the magnitude of the piezoelectric effect. Through measurements of current and voltage in response to an applied mechanical strain via acoustic excitation, we confirmed that piezoelectricity manifests in SnSe films thicker than the expected 2D monolayer limit. A current of 0.5 pA is observed for a 1 mV excitation voltage and increases/decreases with the excitation amplitude of the applied acoustic wave. Ultimately, this dissertation provides the critical processing metric needed for the direct deposition of SnSe for device fabrication and then uses these devices to validate the predicted piezoelectric response. This work serves as a roadmap for the development of 2D piezoelectric and electronics devices based on 2D SnSe.