A phase-change material and a memory unit using the phase-change material are provided. The phase-change material is in a single crystalline state and includes a compound of a metal oxide or nitroxide, wherein the metal is at least one selected from a group consisting of indium, gallium and germanium. The memory unit includes a substrate; at least a first contact electrode formed on the substrate; a dielectric layer disposed on the substrate and formed with an opening for a layer of the phase-change material to be formed therein; and at least a second contact electrode disposed on the dielectric layer. As the phase-change material is in a single crystalline state and of a great discrepancy between high and low resistance states, the memory unit using the phase-changed material can achieve a phase-change characteristic rapidly by pulse voltage and avert any incomplete reset while with a low critical power.