Synthesis, photoluminescence and field emission properties of well aligned/well patterned conical shape GaN nanorods

Abstract

Vertically well aligned, well patterned and high density conical shaped GaN nanorods have been synthesized on a Si substrate by pre-treating the GaN powder with aqueous NH₃via a facile chemical vapor deposition method without any catalyst. The nanorods obtained have been characterized by XRD, EDX, TEM, HRTEM and SAED. The observed diameter of the nanorods is 80–100 nm whereas their sharp tip angle measured is 55°. The calculated number of sharp nanorod tips in 1 mm² is approximately 1.56 × 10⁸, indicating high growth density of nanorods which is crucial for field emission properties. The GaN nanorods have exhibited impressive field emission properties and high stability with a lower turn-on field of 3.35 V μm⁻¹ (0.01 mA cm⁻²) at room temperature which is sufficient for electron emission devices, field emission displays and vacuum nano-electronic devices. Moreover, uniform, well-aligned, well-patterned and high-density growth of GaN nanorods also make them promising candidates for nano-device design and integration in the future. The room-temperature PL emission with a strong peak at 370 nm (3.35 eV) indicates that GaN nanorods have potential application in light-emitting nano-devices. A vapor–solid growth mechanism for GaN nanorods has also been discussed briefly.