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BEGIN:VEVENT
DTSTAMP:20260909T063524Z
LAST-MODIFIED:20160425T161045Z
DTSTART:20160502T160000Z
DTEND:20160502T170000Z
UID:event1597@bu.edu
URL:http://physics.bu.edu/internal/events/show/1597
SUMMARY:Nano-Patterning by Ion Bombardment
DESCRIPTION:Featuring Mahsa Mokhtarzadeh\n\nPart of the Preliminary Oral Ex
	am.\n\nExamining Committee: Karl Ludwig\, Ophelia Tsui\, Anatoli Polkovniko
	v\, Lee Roberts\n\nAbstract:\nThe bombardment of surfaces by ions can lead 
	to the spontaneous formation of nano-structures. Depending on the irradiati
	on conditions\, smoothening or roughening mechanisms can be the leading ord
	er in pattern formation which can result in the creation of dots\, ripples 
	or ultra-smoothening effects.  The fundamental processes governing surface 
	pattern formation are not well understood; therefore\, understanding the ph
	ysical mechanisms of surface evolution during ion bombardment is one of our
	 research goals. Our recent grazing incidence small angle x-ray scattering 
	(GISAXS) measurements of the structure factor of Si surfaces undergoing 1 k
	eV Ar+ ion-bombardment indicate an important role for ion-induced stress as
	 a competing mechanism along with the more recognized impact-induced redist
	ribution and erosion processes for pattern formation.\n Therefore\, stress 
	measurement techniques were also designed and  performed in our lab in orde
	r to measure the stress in Si surfaces irradiated as a function of ion ener
	gy\, flux and angle. \nMoreover\, using new x-ray photon correlation spectr
	oscopy (XPCS) techniques in a coherent GISAXS scattering geometry offers ex
	tensive new opportunities to investigate surface dynamical processes and fl
	uctuations in much greater detail than was previously possible. We have tak
	en advantage of this new capability to perform XPCS studies of silicon surf
	aces under various ion-beam irradiation conditions. The early time as well 
	as the steady state regime of the surface evolution provide us valuable inf
	ormation that can lead to better understanding the mechanisms of pattern fo
	rmation. \n In addition\, I will present the results of simulations of  gro
	wth models such as linear Kuramoto- Sivashinsky (KS) and Kardar-Parisi-Zhan
	g (KPZ) that have been carried out for comparing the temporal correlation f
	unctions of the scattered intensity with the new Co-GISAXS experiments.\n\n
	![Mahsa](/resources/event-image/1597/5d2c899_small)
LOCATION:SCI 352\, 590 Commonwealth Avenue\, 02215
STATUS:CONFIRMED
CLASS:PUBLIC
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