Complex sentence: "Thin" is a relative term, but most deposition techniques allow layer thickness to be controlled within a few tens of nanometres, and some (molecular beam epitaxy) allow single layers of atoms to be deposited at a time.
Split into simpler sentences: Thin is a relative term, but most deposition techniques control layer thickness within a few tens of nanometres. Molecular beam epitaxy allow a single layers of atoms to be deposited at a time.