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CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:1
UID:UW-Physics-Event-8360
DTSTART:20230824T210000Z
DTEND:20230824T223000Z
DTSTAMP:20260414T031203Z
LAST-MODIFIED:20230810T212027Z
LOCATION:5310 Chamberlin
SUMMARY:Defect Identification using Kelvin Probe Force Microscopy and 
 Optimization of Long Single-Channel One-dimensional Quantum Wires\, Gr
 aduate Program Event\, Leah Tom\, Department of Physics Graduate Stude
 nt
DESCRIPTION:The advent of quantum computing has been hailed as the nex
 t industrial revolution because of its promise to solve problems that 
 are beyond the reach of classical computers. In order to harness the p
 otential of quantum computing\, it is important to protect fragile qub
 it states from environmental disturbances. This requires designing mic
 roelectronics with a greater degree of control over their fabrication.
  This thesis describes two projects\, the first of which addresses the
  need for an enhanced understanding of defects in quantum dot qubit sy
 stems\, and the second of which develops long single-channel one-dimen
 sional quantum wires for topological qubits.<br>
\n<br>
\nCharge fluct
 uators in Atomic Layer Deposited (ALD) aluminum oxide represent a majo
 r source of charge noise in quantum dot qubit devices. To mitigate thi
 s charge noise\, the defects that adversely affect qubit operations ne
 ed to be identified so that they can eventually be eliminated from the
  gate oxide. The spatial distribution of the defects in the gate oxide
  needs to be determined to correlate the defects with the charge noise
  measured.<br>
\n<br>
\nTowards this end\, Kelvin Probe Force Microsco
 py (KPFM) measurements are performed on a layer of ALD aluminum oxide 
 grown atop bulk silicon. KPFM measures local variations in the work fu
 nction that reveal a high density of charged defects in the aluminum o
 xide layer. Sweeping the AFM tip-to-sample bias induces charging and d
 ischarging events near the surface\, allowing us to probe the defects'
  different charge states. With the aid of electrostatic simulations\, 
 the charging and discharging energies are extracted as a function of t
 he voltage bias. The sign and magnitude of a charge state can also be 
 determined from KPFM measurements. This thesis presents a method for i
 dentifying point defect distributions down to individual defects in a 
 sample of high defect density.<br>
\n<br>
\nThis thesis also proposes 
 a split gate design for creating long and uniform 1D quantum wires in 
 low disorder systems that will be used for topological quantum computa
 tion using Majorana Zero Modes. This gate design is predicted to incre
 ase the length of a channel in a single conducting mode to 60-75% of l
 ithographic gate length for a range of quantum wire lengths. This thes
 is also discusses how the split gate design prevents the formation of 
 quantum dots in the channel and how to improve the channel’s adiabat
 icity.
URL:https://www.physics.wisc.edu/events/?id=8360
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