Vanadium(IV) oxide (VO₂) is a unique material that undergoes a reversible phase transformation around 68 °C. The material could potentially be used as an energy-efficient coating for windows since its reflectance in the infrared (IR) increases significantly more than in the visible region. Currently, VO₂ is limited by a transition temperature $({\tau }_c)$ that is too high, luminous transmittance that is too low or both. In this study, a transition temperature of 45 °C is achieved for a reactively sputtered, undoped film by restricting grain size to approximately 30 nm. It is concluded that a higher density of grain boundaries (smaller grain size) provides a greater number of nucleating defects which in turn reduces ${\tau }_c$ . Similarly, a higher density of grain boundaries may reduce the hysteresis width (difference between transition temperatures in heating and cooling). Also in this study, a new set of optical performance metrics is proposed in which the solar spectrum is divided into the ultraviolet (UV), visible and near infrared (NIR) regions. This approach is more closely aligned with the goals of limiting UV, allowing luminous and modulating NIR transmission. Using these metrics, the optical properties of the low-${\tau }_c$ sample were: 2% UV transmittance, 47% luminous transmittance, and 23% NIR modulation (decrease from 43 to 33%). This study demonstrates that the grain size of VO₂ should be viewed as an important parameter for controlling the transition temperature of the material.

Nitrogen‐rich titanium nitride (TiN) thin films containing excess nitrogen up to 87.0 at.% were produced on (100) Si substrates via the reactive magnetron DC‐sputtering of a commercially available 99.995 at.% pure Ti target within an argon‐nitrogen (Ar‐N₂) atmosphere with a 20‐to‐1 gas ratio. The process pressure (P_P) and substrate temperature (T_S) at which deposition occurred were varied systematically between 0.26 Pa–1.60 Pa and between 15.0^∘C–600^∘C, respectively, and their effects on the chemical composition, surface morphology, and preferred orientation were characterized by energy dispersive X‐ray spectroscopy (EDS), field emission scanning electron microscopy (FE‐SEM), and X‐ray diffraction (XRD). The EDS analysis confirms increasing nitrogen content with increasing P_P and T_S. The SEM images reveal a uniform and crystallized surface morphology as well as a closely packed cross‐sectional morphology for all crystalline films and a loosely packed cross‐sectional morphology for amorphous films. Films produced at lower P_P and T_S have a pyramidal surface morphology which transitions to a columnar and stratified structure as P_P and T_S increase. The XRD analysis confirms the existence of only the δ‐TiN phase and the absence of other nitrides, oxides, and/or sillicides in all cases. It also indicates that at lower P_P and T_S, the preferred orientation relative to the substrate is along the (111) planes, and that it transitions to a random orientation along the (200), (220), and (311) planes as P_P and T_S increase and these results correlate with and qualify those observed by SEM.