Multi-layer phase change material

A multi-layer phase change material, comprising:

• a multi-layer film structure, said multi-layer film structure comprising a plurality of periodic units, said periodic units each comprising a first single-layer film phase change material and a second single-layer film phase change material, wherein:
• said first single-layer film phase change material and said second single-layer film phase change material are alternately stacked and are in contact with each other;
• each of said first single-layer film phase change material and said second single-layer film phase change material is changeable from an amorphous state to a crystalline state by a first electric pulse and is changeable from the crystalline state to the amorphous state by a second electric pulse;
• said first single-layer film phase change material consists of a first plurality of chemical components;
• said second single-layer film phase change material consists of a second plurality of chemical components;
• said first plurality of chemical components are the same as said second plurality of chemical components and a percent composition of said first plurality of chemical components is different from a percent composition of said second plurality of chemical components;
• a crystal structure of said first single-layer film phase change material and a crystal structure of said second single-layer film phase change material belong to a same lattice system;
• and
• a lattice mismatch between said first single-layer film phase change material and said second single-layer film phase change material is less than 10%.