MSE Masters Thesis Presentation of Benli Jiang

TITLE: STUDIES OF ION BEAM NANOPATTERNING ON SILICON AND POLYMER THIN FILM

ABSTRACT: Ion bombardment can lead to a spontaneous formation of a range of nanopatterns on surfaces, including nanodots, nanoscale ripples, and nanoscale pits or holes. This thesis is mainly focused on the behavior of ripple patterns on silicon surfaces as a function of the ion incidence angle. A preliminary study of ion beam nanopatterning on polymer thin films is also presented in this thesis.

The research on ion beam nanopatterning of silicon is largely motivated by a recent theory predicting the development of well ordered ripples when the ion incidence angle is close to the critical angle. For this study of silicon nanopatterning, initially flat samples were bombarded by a broad beam of 250 eV Ar+ ions with a range of angles (65°-41°) around the critical angle, leading to the spontaneous formation of nanoscale ripples. Atomic Force Microscopy (AFM) topographs show the change of ripples as a function of ion incidence angle. The ripple wavelength and crest length are measured from AFM topographs to quantify the degree of order. The ripple peak width in the AFM Power Spectral Density is also examined. In general, the ripples achieve higher degree of order close to the critical angle. However, the behavior of ripple formation close to the critical angle is more complicated than the theory’s prediction. More studies need to be done to further understand this complex behavior.

For the preliminary study of polymer thin film nanopatterning, initially flat samples were bombarded by 250 eV Ar+ ions at the incidence angles of 0°, 45°, and 65° to study the interaction of ion beams with polymers based on different proposed pattern forming mechanisms. Scanning Electron Microscopy (SEM) and AFM topographs show that several types of interesting patterns formed on the surface of different polymer thin films.

COMMITTEE: Advisor: Karl Ludwig, MSE, Physics; Anna Swan, MSE, ECE; Srikanth Gopalan, MSE, ME

When 1:30 pm on Thursday, April 15, 2021
Location ZOOM