Figure 4
From: Surface modification and coherence in lithium niobate SAW resonators
AFM of various surface prepared LN substrates (a)–(e) 0.5 \(\upmu\)m square, 512 pixel peak-force mode AFM image of unprocessed congruent LN, argon ion milled LN, annealed at 500 \(^{\circ }\) C for 8 hr LN, annealed and BOE dipped LN, and piranha dipped LN. Asterisk on the piranha sample and one CLN sample denote material sourced from a separate area of the wafer. Each image is made on x-cut material, with the X scanning direction of the AFM along crystal Z+30\(^{\circ }\). A change in surface morphology is noticed after annealing, and maintained after BOE dip. (g) The RMS roughness of each material process type; error bars are determined from several AFM images. (h), (i) The histograms of the flattened anneal and anneal + BOE samples. The histograms are fit to a sum of three Gaussian peaks to determine the step heights between atomic terraces. Mean step height of the annealed sample is \(200 \pm 80\, \text {pm}\), and \(240 \pm 80\,\text {pm}\) for annealed + BOE. Uncertainty is set by the fit standard deviation of the Gaussian peaks.
