We report an ultrahigh-density ferroelectric data recording system based on purely electrical principles, using a scanning nonlinear dielectric microscopy technique and ferroelectric thin films of LiTaO3 single crystals. A nano-sized domain dot array of areal density of 1.50 Tbit inch-2 has been successfully demonstrated in a z surface of a congruent LiTaO3 single-crystal film. The radius of the domain dots was 10.4 nm. These nano-dots remained stable at least over 24 h, and could be over-written by dots. The ferroelectric domain inversion characteristics using a stoichiometric LiTaO3 single-crystal film was also studied. A very small nano-sized domain dot with a radius of 6 nm was successively formed.