Plasma-Enhanced Atomic Layer Deposition of Nanostructured Gold Near Room Temperature

Abstract

A plasma-enhanced atomic layer deposition (PE-ALD) process to deposit metallic gold is reported, using the previously reported Me 3 Au(PMe 3) precursor with H 2 plasma as the reactant. The process has a deposition window from 50 to 120°C with a growth rate of 0.030 ± 0.002 nm per cycle on gold seed layers, and it shows saturating behavior for both the precursor and reactant exposure. X-ray photoelectron spectroscopy measurements show that the gold films deposited at 120°C are of higher purity than the previously reported ones (<1 at. % carbon and oxygen impurities and <0.1 at. % phosphorous). A low resistivity value was obtained (5.9 ± 0.3 μΩ cm), and X-ray diffraction measurements confirm that films deposited at 50 and 120°C are polycrystalline. The process forms gold nanoparticles on oxide surfaces, which coalesce into wormlike nanostructures during deposition. Nanostructures grown at 120°C are evaluated as substrates for free-space surface-enhanced Raman spectroscopy (SERS) and exhibit an excellent enhancement factor that is without optimization, only one order of magnitude weaker than state-of-the-art gold nanodome substrates. The reported gold PE-ALD process therefore offers a deposition method to create SERS substrates that are template-free and does not require lithography. Using this process, it is possible to deposit nanostructured gold layers at low temperatures on complex three-dimensional (3D) substrates, opening up opportunities for the application of gold ALD in flexible electronics, heterogeneous catalysis, or the preparation of 3D SERS substrates.

Reaction mechanism of the Me3AuPMe3–H2 plasma-enhanced ALD process

“…A home-built pump type ALD reactor, with a base pressure of 2x10 -6 mbar, is used to carry out all atomic layer depositions, unless stated otherwise. 3 The Me 3 AuPMe 3 precursor (≥95% purity) is synthesised via the method used by Griffiths et al 1 The (CD 3 ) 3 Au(PMe 3 ) precursor (≥95% purity, and >99% deuteration) is synthesised as described in the paper of Shaw and Tobias. 10 The purity of the precursor liquids is verified by NMR measurements (see Supporting Information).…”

“…This is reflected by the existence of only three gold ALD processes. [1][2][3] In contrast there exists a large list of CVD processes using several different types of gold complexes to deposit gold films. 4 In this paper we will focus on the recently introduced ALD processes that make use of trimethylphosphinotrimethylgold(III) (Me 3 AuPMe 3 ) as the gold precursor which has been used as a CVD precursor before.…”

“…The other Me 3 AuPMe 3 based ALD process uses H 2 plasma as the co-reactant. 3 This process allows the deposition of metallic gold over a broad temperature range from 50 • C to 120 • C with a growth rate of 0,030±0,002 nm per cycle. The reaction mechanism has not been studied in detail.…”

Mitigation of photon background in nanoplasmonic all-on-chip Raman sensors

“…More advanced mode matching at those three critical points will ultimately reduce the reflection and therefore improve the performance of our MMI-based circuit. For instance, the reflection due to the plasmonic waveguide could be better controlled by a more precise deposition technique such as the atomic layer deposition of gold that furthermore results in an increased Raman response [27]. Another way to improve the architecture is to engineer the MMI so that it acts as a wavelength division multiplexer [28,29] transmitting the excitation beam from a port 1 to 3 with a high transmission and transmitting it inefficiently from port 3 to port 2 while the scattered Raman light is collected in port 3.…”

Behavior of Muscle-Derived Stem Cells on Silica Nanostructured Substrates

“…Several studies have tested cellular responses to nanoscale topographic substrates, showing that the contact of different human tissues with nanostructured substrates can influence cellular responses in biomedical applications [ 1 , 2 , 3 , 4 ]. Studies performed to date have reported that various nanostructured substrates can modulate the adhesion and proliferation of different mammalian cell types [ 5 , 6 ].…”