Manipulation of thin metal film morphology on weakly interacting substrates via selective deployment of alloying species

Abstract

We demonstrate a versatile concept for manipulating morphology of thin (≤25 nm) noble-metal films on weakly interacting substrates using growth of Ag on SiO2 as a model system. The concept entails deployment of minority metallic (Cu, Au, Al, Ti, Cr, and Mo) alloying species at the Ag-layer growth front. Data from in situ and real-time monitoring of the deposition process show that all alloying agents—when deployed together with Ag vapor throughout the entire film deposition—favor two-dimensional (2D) growth morphology as compared to pure Ag film growth. This is manifested by an increase in the substrate area coverage for a given amount of deposited material in discontinuous layers and a decrease of the thickness at which a continuous layer is formed, though at the expense of a larger electrical resistivity. Based on ex situ microstructural analyses, we conclude that 2D morphological evolution under the presence of alloying species is predominantly caused by a decrease of the rate of island coalescence completion during the initial film-formation stages. Guided by this realization, alloying species are released with high temporal precision to selectively target growth stages before and after coalescence completion. Pre-coalescence deployment of all alloying agents yields a more pronounced 2D growth morphology, which for the case of Cu, Al, and Au is achieved without compromising the Ag-layer electrical conductivity. A more complex behavior is observed when alloying atoms are deposited during the post-coalescence growth stages: Cu, Au, Al, and Cr favor 2D morphology, while Ti and Mo yield a more pronounced three-dimensional morphological evolution. The overall results presented herein show that targeted deployment of alloying agents constitutes a generic platform for designing bespoken heterostructures between metal layers and technologically relevant weakly interacting substrates.

Chemical Stability of Sputter Deposited Silver Thin Films

“…The violet markers are used for this work (full and open marker for non-seeded and seeded layer, respectively). Data taken from: (1) [39], (2(Ge)) [40], (3) [41], (4(Cu)) [42], (5) [43], (6) [44], (7) [45], (8) [46], (9) [47], (10) [48], (11) [49], (12) [50], (13) [51], (14) [52], (15) [53], (16) [54], (17) [55], (18) [56], [19(ZnO)] [57], (20) [58], (21(CuO)) [59], (22) [60], and (23) [61].…”

“…Therefore, strategies have been developed to overcome this problem. Silver can be alloyed with other elements [10][11][12][13][14]. Additionally, the use of gaseous surfactants has been reported [12,15,16].…”

Low-E glass improvement by the understanding and control of the Ag growth

“…[12,13] Jamnig et al have shown that Ag alloyed with metals (Cu, Al, Au or Cr) can be used at the very beginning of the growth to promote subsequently 2D Ag growth avoiding a large increase of the resistivity. [14] To avoid the small-grains film, a ZnO or Al-doped ZnO (AZO) are generally the preferred seed layer because their growth along c-axis promotes Ag growth along (111). [15,16] It has been shown that 5 nm of AZO is beneficial to promote heteroepitaxy growth [15].…”

Near-Zero Transmittance Loss, Highly Durable, Flexible, Transparent Electrode with an Ultrathin Ag Nanoporous Structure

“…Surface plasma resonance occurs and deteriorates the performance of OMO TEs owing to wavelength-dependent absorption and scattering when Ag is dispersed as nanoparticle arrays, which evolve in the initial growth stages. , In contrast, the absorbance and reflection of incident light are aggravated with further increases in Ag thickness over the minimum thickness for continuous layered geometry . Currently available techniques for implementing ultrathin continuous Ag layers rely heavily on wetting inducers, such as metallic dopants, − metallic seeds, − oxide seeds, − and gaseous dopants, ,− as thoroughly surveyed in a previous review . However, these techniques are still rigorously challenged by the crucial question of whether the fabrication of an ideal 2D Ag layer with complete elimination of nanopores (or voids) can be achieved at an ultralow thickness of a few nanometers.…”