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Atomistic disorder effects on structural, electronic and phononic properties in Si1-xGex

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Title: Atomistic disorder effects on structural, electronic and phononic properties in Si1-xGex
Author(s): Hossain, Md Z.
Director of Research: Johnson, Harley T.; Freund, Jonathan B.
Doctoral Committee Chair(s): Johnson, Harley T.; Freund, Jonathan B.
Doctoral Committee Member(s): Aluru, Narayana R.; Sinha, Sanjiv
Department / Program: Mechanical Sci & Engineering
Discipline: Mechanical Engineering
Degree Granting Institution: University of Illinois at Urbana-Champaign
Degree: Ph.D.
Genre: Dissertation
Subject(s): phonons quantum confinement atomistic disorder ion bombardment sputtering ripple formation interatomic potential alloy quantum dot
Abstract: While single crystalline materials such as Si dominate a myriad of applications, alloy materials like Si1-xGex are becoming increasingly attractive because of their enhanced material properties. Their intriguing material properties originate from the distribution of constituent species that depends on a number of factors, such as temperature, strain, chemical miscibility, degree of segregation etc. Determining the distribution of atoms on the angstrom level length scale and finding their correlation with fundamental material properties experimentally is a challenging task. On the other hand, with the outstanding predictive power of the computational resources available nowadays, a wide variety of complex processes involving the distribution of atoms can be modeled using a combination of atomistic and continuum methods. To meet the growing demand for finding new materials it is crucial to explore new insights such that material properties can be tailored at the level of electrons, atoms or photons. Taking Si1-xGex (which is a very important material system for numerous applications) as an example alloy material, this thesis research aims to provide a broad investigation on the influence of atomistic arrangement on a range of material properties including structural, electronic and phononic properties. It is found that the arrangement and rearrangement of atoms plays an important role on governing its fundamental material properties and mechanisms. For example, first principles simulations show that atomic scale variations in composition field affect (a) quantum confinement in Si1-xGex/Si quantum dots and make larger quantum dots function like smaller quantum dots and (b) sensitivity of optical phonons that can significantly baffle the interpretation of Raman measurements. On the other hand, the underlying mechanisms for the evolution of morphological orientation in ion-bombarded Si and Ge surfaces originate from the rearrangement of atoms during the femtosecond atomic collisions. Additionally, distribution of the energetic particles on an ion bombarded surface relates closely with the local sputtering from the surface.
Issue Date: 2011-08-25
URI: http://hdl.handle.net/2142/26196
Rights Information: Copyright 2011 Md Z. Hossain
Date Available in IDEALS: 2011-08-25
Date Deposited: 2011-08
 

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