Pulsed Laser Deposition of 2D materials and Complex Perovskites

• Author / Creator

  Gudi, Dhanvini

• Pulsed laser deposition is a physical vapor deposition technique used for the growthof single crystal epitaxial thin films on a variety of substrates. Due to the high en-ergy of the ablated particles from the target, the plasma plume consists of atoms,molecules, ions and electrons, PLD allows for high efficiency in the deposition ofmaterials with complex stoichiometry.Two very different materials are grown using PLD in this study, namely, a 2D ma-terial called Molybdenum sulphide (MoS2) for electronic device applications and anovel perovskite material called for La0.3M0.7Fe0.7Cr0.3O3-δ(M = Ca, Sr) (LCFCrand LSFCr) for solid oxide fuel cell applications. This thesis consists of a studyof the effect of the variation of PLD parameters on the film quality, and thus, anoptimization of these parameters to obtain thin films with desirable properties.The thin films of MoS2grown in different conditions have been analyzed usingmaterial and electronic characterization techniques to study the film properties.Single crystal epitaxial growth was obtained with a crystal phase correspondingto (002) orientation of MoS2. A high uniformity with a film RMS roughness ofaround 0.17 nm was obtained for 5 monolayers of MoS2. XPS analysis was usedto observe a presence of small amounts of MoO3and semimetallic 1T-MoS2in thesemiconducting 2H-MoS2thin films. Transmission and absorption studies over dif-ferent thicknesses of the deposited films showed the presence of B and C excitonictransitions in the film.

  Hall measurement has also been performed for the thin films over different thick-nesses to study electrical properties. With Van der Pauw measurements over anarea of around 25 mm2, an increasing trend was observed from 5 to 13 monolay-ers of MoS2and a decreasing trend from 13 to 56 monolayers of MoS2, with thehighest electron mobility of 76.92 cm2/Vs observed in our studies for 13 mono-layers of MoS2. This trend matched the studies of FET mobility measured overdevices with different thicknesses observed in literature. These promising studiessuggest potentially higher mobilities on PLD grown MoS2thin film based FETdevices. These studies serve as a starting point for several future applications ofPLD deposited MoS2thin films in scaled electronic devices and sensors and flexibleelectronic devices and sensors.Thin films of LMFCr (LCFCr and LSFCr) were deposited under different condi-tions and analyzed using using material characterization techniques to study thefilm properties. Under optimized growth conditions, epitaxial single crystal thinfilms of LCFCr with a (002) crystal phase was observed. A high film uniformity with the lowest RMS roughness of 0.15 nm obtained for LCFCr. XPS analysis helped study and confirm the elemental states present in the thin films. These optimized thin films can be used for solid oxide fuel cell applications in the future

• Subjects / Keywords

  • pulsed laser deposition thin film deposition mos2 lcfcr

• Graduation date

  Spring 2020

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-fc2d-5p47

• License

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