Impact of high substrate temperature on pulsed laser deposited ZnO pillars: A technological route to investigate the structural, optical and superhydrophilic properties

The structural, optical, and superhydrophilic properties of zinc oxide (ZnO) pillars are reported by pulsed laser deposition (PLD) technique at a high substrate temperature of 700 °C. The X-ray diffraction (XRD) analysis reveals that the increased crystallite size in ZnO-700 (98.47 nm) plays an important role in promoting superhydrophilic behaviour than ADZnO-RT (57.19 nm). The root-mean-square surface roughness (R r.m.s ) from scanning probe microscope (SPM) analysis demonstrates the significant enhancement in ZnO-700 surfaces. The ZnO-700 based samples show improved light absorption in the ultra-violet (UV) and visible light absorption which can boost photocatalytic activity. The photoluminescence (PL) analysis shows the highest (zinc) Zn interstitial (Zn i ) and lowest oxygen vacancy (O V ) concentration in ZnO-700. A static contact angle (CA) measurement was performed, where ZnO-700 sample displays a smaller static CA (98.60°) compared to ADZnO-RT (101.90°), indicating more superhydrophilic nature. The ZnO-700 based sample had a better sliding angle ( α ) of 61.65°, a maximum frictional force ( Fmax ) of 1.76 μN, a corresponding work of adhesion ( Wadhesion ) 61.01 mN/m, and a wettability conversion rate (WCR) of 7.20 × 10 −5 ° −1 /min indicating fast sliding phenomena and better superhydrophilic transition. The superhydrophilic properties of ZnO-700 make it a valuable asset for smart surfaces and microfluidic devices application.