Many instruments and equipments (AFM, PLL, amplifiers and etc.) are commercially available for Akiyama-Probe operation. They are very reliable and highly recommended to use.
A self-oscillation circuit can be built with some OP-amps. In a simple case, the PLL can be outside of the self-oscillation loop and works in a passive mode. If a single chip PLL (e.g., 4046) is used, a complete setup can be built with a low budget. If a higher resolution is required in this configuration, the simple PLL can be replaced with a more accurate commercial PLL without any major modification of the setup.
Laboratory standard instruments + minimum analog electronics:
One can make a high resolution “self-oscillation + PLL” setup with two standard laboratory instruments (lock-in amplifier and frequency synthesizer) and a very simple analog circuit. The analog circuit with a few OP-amps forms a proportional-integral gain controller.