BS in Materials Engineering
Materials Engineering Department
The electrical surface structure of (111) n-type silicon was investigated through the use of scanning tunneling spectroscopy (STS) to develop a model to determine oxide presence on a passivated silicon surface. I-V curves were obtained with a scanning tunneling microscope (STM) using a tungsten tip on various locations of passivated silicon while the passivation layer desorbed from the surface under standard atmospheric conditions. The derivative (dI/dV) of these curves then revealed the electronic structure of the surface of the sample. Through these scans, it was determined the system was operating in the same mode as a Shockley diode. The separation of the band energies between the tungsten tip and n-type silicon created a Shockley diode with a barrier height of 0.45 V that was verified with the dI/dV curves. The scans obtained showed a general shift in surface properties through a shift in the width and location of the conductance peaks as the scan time progressed. The shifts suggest an oxide growth due to the change in electrical structure or local density of states (LDOS) over time.