A thin-film disk is a hard disk storage medium with a very thin coating of a metallic alloy or glass instead of the usual carbon-based material found on other types of hard disks. The thin film lets the read/write head get closer to the surface, allowing more data to be stored in a given space.
Thin-film technology is another approach to packing more bits of data onto a disk. As the number of data bits on a disk increase, the disk drive's head must become more sensitive, getting closer to the disk to read or write the bits.
Researchers are experimenting with thin films of various materials in order to help protect the disk from the head and to help the disk have a longer life.