There are provided (a) heat-treating a substrate including a film containing a group 14 element at a first temperature; (b) heat-treating the substrate at a second temperature higher than the first temperature; and (c) exposing the substrate to a treatment agent containing at least one of O and H after performing (a) and before performing (b).

A method of manufacturing a display device includes forming a first amorphous silicon layer on a substrate on which a first area and a second area are defined, forming a mask in the second area on the first amorphous silicon layer, forming a preliminary second amorphous silicon layer on the first amorphous silicon layer and the mask, forming a second amorphous silicon layer by removing a portion of the preliminary second amorphous silicon layer on the mask, removing the mask, and forming a polycrystalline silicon layer by crystallizing the first amorphous silicon layer and the second amorphous silicon layer.

A preparation method of an aluminum nitride (AlN) composite structure based on a two-dimensional (2D) crystal transition layer is provided. The preparation method includes: transferring the 2D crystal transition layer on a first periodic groove of an epitaxial substrate; forming a second periodic groove staggered with the first periodic groove on the 2D crystal transition layer; depositing a supporting protective layer; depositing a functional layer of a required AlN-based material; and removing the 2D crystal transition layer through thermal oxidation to obtain a semi-suspended AlN composite structure. The preparation method has low difficulty and is suitable for large-scale industrial production. Design windows of the periodic grooves and the AlN functional layer are large and can meet the material requirements of deep ultraviolet light-emitting diodes (DUV-LEDs) and radio frequency (RF) electronic devices for different purposes, resulting in a wide application range.

Provided are high quality metal-nitride, such as aluminum nitride (AlN), films for heat dissipation and heat spreading applications, methods of preparing the same, and deposition of high thermal conductivity heat spreading layers for use in RF devices such as power amplifiers, high electron mobility transistors, etc. Aspects of the inventive concept can be used to enable heterogeneously integrated compound semiconductor on silicon devices or can be used in in non-RF applications as the power densities of these highly scaled microelectronic devices continues to increase.