Mechanism and characteristics of the new organic nonlinear optical material urea L-malic acid film

A new nonlinear optical material urea L-malic acid film (ULMA) was successfully prepared by physical vapour deposition (PVD) at appropriate heating temperature. XRD and FTIR measurements show that the film and the ULMA powder have the same composition and crystal structure. Furthermore, the film keeps the nonlinear properties of the ULMA crystal. Thermal analysis shows that ULMA has good thermal stability with constant melting point. Its evaporation temperature is below the decomposition temperature of its substrates urea and L-malic acid. The difference between evaporation and decomposition temperature is increased in vacuum. Therefore, it is verified that the PVD method is a practical approach to prepare ULMA film if the heating temperature is controlled between the evaporation and decomposition temperatures.