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PhD Preliminary Oral Exam – Kamesh Mullapudi

Investigation into Atomic layer Deposition of 2D WS2 using a novel precursor and Area selective deposition using an new aj-fog mist deposition system

2D transition metal dichalcogenides (TMDCs) such as Tungsten disulfide, known for its semiconductor like bandgap and high mobilities, have attracted interest in recent years as an alternative to graphene. Popular synthesis methods such as mechanical exfoliation and chemical vapor deposition (CVD) have been demonstrated to synthesize crystalline films with grain sizes of up to a few microns and show good electrical properties, but lack scalability and precise layer thickness control, respectively. Atomic layer deposition (ALD) is an ideal technique for achieving highly conformal and uniform films with the layer by layer thickness control needed for these applications but faces challenges in achieving high crystallinity. In this work, we report ALD of WS2 films using a novel precursor metal-organic tungsten precursor (WSN-4) and H2S. Further, crystallites as large as 1μm have been grown by annealing these ALD films in elemental sulfur at 600C and above. In addition, we also investigate a new, zero-waste, aerosol jet fog (ajFOG) deposition system is for controlled area-selective deposition of Aluminum oxide phosphate films from an aqueous precursor, at room temperature and pressure. Area selective deposition is accomplished using octyl-trichlorosilane (OTS-8) self-assembled monolayers which form a blanket hydrophobic functionalization of SiO2/Si (100) substrates. Excellent control in selective depositions are demonstrated by achieving different shapes with high edge acuity in the form of circles, squares, lines, and 90° angles. The presence of surface energy gradient around the feature plays an important role in influencing its size and height. This technique shows promise potential applications in process technologies “More than Moore”, such as fabrication of MEMS and large flat panel displays.

Major Advisor: John Conley, Jr.
Committee: Larry Cheng
Committee: John Labram
Committee: Matt Graham
Committee: Rafik Addou
GCR: Adam Higgins

Wednesday, March 4, 2020 at 11:00am to 1:00pm

Kelley Engineering Center, 1005
110 SW Park Terrace, Corvallis, OR 97331

Event Type

Lecture or Presentation

Event Topic


Electrical Engineering and Computer Science
Contact Name

Calvin Hughes

Contact Email

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