Abstract
Silica nanosprings (NS) were coated with gallium nitride (GaN) by high-temperature atomic layer deposition. The deposition temperature was 800 °C using trimethylgallium (TMG) as the Ga source and ammonia (NH3) as the reactive nitrogen source. The growth of GaN on silica nanosprings was compared with deposition of GaN thin films to elucidate the growth properties. The effects of buffer layers of aluminum nitride (AlN) and aluminum oxide (Al2O3) on the stoichiometry, chemical bonding, and morphology of GaN thin films were determined with X-ray photoelectron spectroscopy (XPS), high-resolution x-ray diffraction (HRXRD), and atomic force microscopy (AFM). Scanning and transmission electron microscopy of coated silica nanosprings were compared with corresponding data for the GaN thin films. As grown, GaN on NS is conformal and amorphous. Upon introducing buffer layers of Al2O3 or AlN or combinations thereof, GaN is nanocrystalline with an average crystallite size of 11.5 ± 0.5 nm. The electrical properties of the GaN coated NS depends on whether or not a buffer layer is present and the choice of the buffer layer. In addition, the IV curves of GaN coated NS and the thin films (TF) with corresponding buffer layers, or lack thereof, show similar characteristic features, which supports the conclusion that atomic layer deposition (ALD) of GaN thin films with and without buffer layers translates to 1D nanostructures.
Highlights
Atomic layer deposition (ALD) is an extremely valuable technique for growing conformal and precision ultrathin films for transistors, light emitting diodes [1,2], capacitors [3,4], solar cells [5,6], as well as different types of storage media, such as dynamic random-access memory (DRAM) and hard disk drives (HDD) [7,8], and recently solid-state batteries [9,10]
The absence of the C 1s core level state in the survey scan of the sputtered surface demonstrates that C was only at the surface or that the subsurface C concentration is below the resolving power of X-ray photoelectron spectroscopy (XPS)
The (002) and (102) Bragg peaks of gallium nitride (GaN) are observed in the high-resolution x-ray diffraction (HRXRD) spectra, where the (102) peak is attributed to stress in the films and indicate that the thin film growth is in the c-axis direction
Summary
Atomic layer deposition (ALD) is an extremely valuable technique for growing conformal and precision ultrathin films for transistors, light emitting diodes [1,2], capacitors [3,4], solar cells [5,6], as well as different types of storage media, such as dynamic random-access memory (DRAM) and hard disk drives (HDD) [7,8], and recently solid-state batteries [9,10]. Due to the excellent surface conformation of ALD coatings, it is ideally suited for coating complex nanostructures. The desire to develop nanostructures with technologically important coatings like GaN dictates that ALD processes be developed for coating complex nanostructures. The same can be said for ALD deposition systems. Many commercially available ALD systems are not designed to operate at high temperatures. This is necessary for obtaining high-quality GaN and other more exotic materials. With this in mind, we begin by exploring existing reviews of ALD to elucidate the advantages, disadvantages, and deposition system designs [17,18]
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