Abstract:
This paper reports the facile synthesis of tunable hydrophobic and colossal antireflective nanoporous GaSb by alteration of its porosity. In particular, it is observed that the contact angle of a water droplet on the GaSb surface increases as the nanoporous structures undergo different stages of growth and finally exceeds 150 degrees, indicating the transition to a superhydrophobic surface. The observed correlation between the contact angle and the surface morphology is qualitatively understood in light of the Cassie-Baxter model. It is found that with the temporal evolution of nanostructures, a decrease in the fraction of the solid surface wetted by the water droplet and a corresponding increase in the air-water interface fraction lead to the enhancement in hydrophobicity, where the chemistry of the porous surface also plays a role. The temporal evolution of the contact angle is also studied to understand the interaction of the sessile drop with the hydrophobic surface and the ambient. In addition to an increase in the contact angle, we also observe a colossal broadband antireflection (in the range of 200-800 nm), which is correlated to a large reduction in the refractive index due to increasing porosity. Such a surface, with the combination of superhydrophobicity and colossal antireflection, can be very useful in the applications of GaSb nanostructures in thermophotovoltaic cells or photodiodes.