Study On An AFM Head With Functions Of In-situ Nanomechanical Measurement And Length Traceability

Nanomechanical test tools include nanoindentation/scratch instruments andatomic force microscopy, etc. In these instruments, samples are indented or scratchedand an AFM is usually used off-line to scan the scratched area. There is not doubt thatit is quite difficult for the AFM to find the scratched area. AFM’s core parts are theprobe and the displacement detection unit. Most commercial AFMs don’t have acalibrated length sensor. The probe’s displacement, which is calculated by the voltageapplied to the piezoelectric ceramic tube, is not accurate enough for mostNano-mechanical tests.In this thesis, an AFM head with functions of in-situ testing and length tracebilityusing a capacitive position sensor is developed. Immediately after a nanomechanicaltest, the AFM head can scan the indented area without moving the sample or theprobe, so an in-situ nano-mechanical test can be performed. The AFM head includes aprecision drive unit, which is composed of a piece of a flexible hinge andpiezoelectric ceramics, a ring capacitance sensor and an optical system. The probe’smaximum displacement is3um. The resolution of the AFM head is better than10nm.The maximum displacement and the resolution can well meet the requirements ofmechanical testing.The main contents of the thesis are listed as the followings:1. Various instruments used for nanomechanical test instruments, such asnanoindentaion/scratch instrument, atomic force microscopy, scanning electronmicroscopy, are reviewed and compared with each other. A new AFM head with thefunction of in-situ mechanical test and length traceability is suggested. Theimportance, aims and main contents of the thesis are described.2. A flexure hinge structure is designed and optimized by using ANSYS softwarefor the analysis of the structured’s statics and dynamics characteristics.3. A ring capacitor sensor with a centered hole is designed and optimized byusing ANSYS software for the analysis of its electrostatic characteristics.4. A high-voltage driver circuit and a sensor signal conditioning circuit aredesigned for the driving unit and displacement detection unit of the AFM head. 5. A software program based on Labview platform is designed for the AFMhead.6. Experiments were conducted to test the sensitivity, linearity and resolution ofthe AFM, and the results were analyzed.