Effect of gas flow rate on structural properties of zinc oxide nanowires grown by vapor-solid mechanism

ZnO nanowires have been grown on pre-coated (ZnO thin film) silicon (100) substrates with special attention on the effect of gas flow rate. The samples were fabricated using a simple thermal evaporation method within a horizontal quartz tube under controlled supply of Ar and O2 gas where ZnO powder source were previously weighed and heated at 960 °C for 2 h, allowing the reactant vapors to deposit onto substrate to form the nanowires. FESEM images revealed the randomly-oriented nanowires in which the shapes varied with increasing gas flow rates from varied from 90 to 130 sccm. According, both diameter and aspect ratio of the nanowires was observed to shift at 110 sccm where optimum growth condition was expected at this gas flow rate. From EDX spectrum analysis, ZnO nanowires appeared to have uniform composition and purity and confirming the hexagonal wurtzite crystal structure. These measured parameters in combination with unique properties made the possibility of ZnO nanowires potentially useful for functional nanodevices.