Abstract
We report response of photoluminescence (PL) from GaN nanowires without protection in solutions. The distinct response is not only toward pH but toward ionic concentration under same pH. The nanowires appear to be highly stable under aqueous solution with high ionic concentration and low pH value down to 1. We show that the PL has a reversible interaction with various types of acidic and salt solutions. The quantum states of nanowires are exposed to the external environment and have a direct physical interaction which depends on the anions of the acids. As the ionic concentration increases, the PL intensity goes up or down depending on the chemical species. The response results from a competition of change in surface band bending and charge transfer to redox level in solution. That of GaN films is reported for comparison as the effect of surface band bending can be neglected so that there are only slight variations in PL intensity for GaN films. Additionally, such physical interaction does not impact on the PL peaks in acids and salts, whereas there is a red shift on PL when the nanowires are in basic solution, say NH4OH, due to chemical etching occurred on the nanowires.
Highlights
Crystalline GaN has been chosen as a promising semiconductor material with a wide direct bandgap of 3.39 eV
Synthesis of GaN Nanowires and Films The growth of GaN nanowires via VSS mechanism and GaN films were fabricated in a hydride vapor phase epitaxy (HVPE) system [44, 45], where the vacuum level is at 1 atmosphere
We investigated the impact of basic solution, e.g., ammonium hydroxide solution (NH4OH), on GaN nanowires for comparison through the PL response
Summary
Crystalline GaN has been chosen as a promising semiconductor material with a wide direct bandgap of 3.39 eV. One-dimensional nanostructures exist intrinsically efficient lattice relaxation [9] They can be grown with less crystal defects [10], and this composes the main benefit where photoluminescence (PL) emission and electrical properties are affected by these defects. For solid-state materials, the interaction of PL with the surrounding chemical conditions provides a way to probe the excited states. Such surface interaction can be used for chemical sensors and imaging [15, 16]. The interaction between the chemicals in solution and the quantum state becomes weak due to the protection
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