GB/T 32189-2015Test method for surface roughness of GaN single crystal substrate by atomic force microscope (English PDF)

4.1 Test Principle

This standard test sample AFM 3D surface topography of an area, and then included in the surface topography according to a set of tables

Numerical evaluation of surface roughness profile. Since the resolution of the atomic force microscope (i.e., vertical resolution) in the height direction usually not more than 0.1nm,

Generally horizontal resolution up to 10nm, so they can be clearly distinguished atomic steps on a single crystal substrate (step height is usually < 1nm), is the assessment

Price effective means single crystal substrate roughness.

Principle of AFM surface roughness of the test sample is shown in Fig. When the test sample surface morphology, first through a coarse approximation means

Set close to the tip and the sample from several nanometers, thus producing interaction. AFM contact mode, tapping mode and other

Operating modes probe tip and the sample interaction force. In contact mode, for example, direct contact with the probe and the sample, the interaction force suspension

Beam arm is deformed so as to be detected by the laser and the optical lever quadrant photodetector constituted. When the sample by the scanning signal generator

When the station to generate xy direction, through the feedback controller controls the level z of the sample, so that deformation of the cantilever arm is always kept constant, the output z

Changes in surface topography is to test. If tapping mode, through a vibration exciter makes Izod generate several nanometers to tens of nanometers vibrator

Vibration amplitude when the tip and sample interaction force generated close to each other, will change the vibration amplitude and phase by feedback control scanning

Z height control sample, maintaining constant vibration amplitude, you can get the output z surface topography.