Refractive index (n) and extinction coefficient (k) of Zn 3 N 2 layers deposited by radio-frequency magnetron sputtering at temperatures (T s ) between 298 and 523 K were determined by spectroscopic ellipsometry. Results showed strong variations of the apparent optical constants with T s and time attributed to surface effects. Resonant Rutherford backscattering and spectroscopic ellipsometry confirmed the formation of a ZnO surface layer provoked by the ambient exposure. Samples grown at low T s presented the lowest surface roughness and exhibited 2.0 < n < 2.8 and 0.6 < k < 1.0 in the 1.5-4.5 eV energy range. The extracted n and k values accurately reproduced the reflectance properties. Zinc nitride (Zn 3 N 2 ) is a promising material for application in electronics and optoelectronics due to its high electron mobility and conductivity. Electrical studies in Zn 3 N 2 showed similar mobility and resistivity values to those obtained in poly-Si (at the same carrier concentration) and even better than in a-Si.1 Moreover, the low cost of its elements and synthesis procedure makes Zn 3 N 2 an excellent choice for mass production in electronic systems. Thus, Zn 3 N 2 is recognized as a potential substitute of Si for the fabrication of thin film transistors along with other materials such as graphene or ZnO. Furthermore, it has been demonstrated the possibility of transforming Zn 3 N 2 into p-type ZnO by thermal treatment in oxidizing ambient, which enables the fabrication of ZnO p-n homojunctions for the development of ultraviolet light emitters. 5 The oxygen content varied depending on the surface properties, as found by means of surface analysis techniques such as Auger electron spectroscopy and x-ray photoelectron spectroscopy. Although optical constants have been determined in the past, 1,6 the impact of surface effects such as surface roughness or the formation of native oxide on the calculated parameters has not been discussed yet. Therefore, it is important to analyze the changes introduced by those on the apparent optical characteristics of the Zn 3 N 2 films. Ellipsometry is an effective tool to rapidly detect morphology and chemical modification of materials over time.
7This work provides insight on the relationship between surface effects and the optical properties of Zn 3 N 2 layers using resonant Rutherford backscattering (RBS), scanning electron microscopy (SEM), spectroscopic ellipsometry (SE), and reflectance spectroscopy (RS). SE was used to determine the optical constants, i.e., refractive index (n) and extinction coefficient (k), of zinc nitride layers and RS helped to confirm their values.Zn 3 N 2 layers were prepared from a pure Zn (99.995%) plasma sputtered target using N 2 (99.999% purity) as working gas. N 2 gas was introduced through a mass flow controller. To study the effect of growth temperature (T s ), five samples were synthesized at T s between 298 and 523 K on Si(100) and glass substrates keeping a constant chamber pressure of 1 Pa by adjusting the pumping rate with a throttle valve. The...