MICROSTRUCTURAL AND SURFACE MORPHOLOGICAL EVOLUTION DURING THIN FILM GROWTH

Joe Greene, University of Illinois

This course covers the basic physics and chemistry, as well as the technology, of thin film crystal growth from the vapor phase. While the emphasis will be on materials used in microelectronics and optoelectronics, examples from other thinfilm based fields including optics, magnetic and optical recording, wear and corrosion protection, superconductivity, and micromechanics will be discussed. Progress in each of these areas depends upon the ability to selectively deposit thin films (thicknesses ranging from tens of Å to Ám) with specified physical properties. This, in turn, requires atomic-level control of film microstructure (e.g., epitaxial, polycrystalline with a given morphology and preferred orientation, or amorphous) and microchemistry (e.g., alloys, abrupt doping distributions, superlattices, metastable phases). Recent progress in atomicscale engineering based upon insights obtained using scanning tunneling microscopy, electron energy loss spectroscopy, and other nanoscale probes will be discussed in detail. Experimental and computer simulation results will be compared.

Course Outline

1. Kinetics of surface processes on metals and semiconductors

a. Surface structure, reconstruction, and roughening transitions

b. Adsorption/desorption kinetics

i. Isotherms and surface phase diagrams

2. Film nucleation and growth

a. Nucleation theory: thermodynamics/kinetics; experiment, models, simulations

i. 2D (step-flow, layer-by-layer, multilayer; terrace size distributions,

adatom step crossing, step-step interactions, surfactants)

ii. Stranski-Krastanov (interfacial strain vs excess surface energy, surface

roughening)

iii. 3D (kinetic, clustering, coalescence)

b. Fundamental limits to epitaxial growth; kinetic roughening

c. Heterostructures: pseudomorphic growth, critical thickness

d. Microstructure evolution in polycrystalline films: coalescence, atomic

shadowing, columnar structures, grain growth, preferred orientation,

structure-zone models

e. Role of low-energy ion/surface interactions; hyperthermal species