Ballistic deposition model with surface diffusion for thin film growth on patterned substrates

In nonequilibrium surface growth processes, such as molecular beam epitaxy and chemical vapor deposition, kinetic roughening plays a significant role in determining surface morphology. The stochastic dynamics in the processes induce novel scaling in surface roughness with respect to growth time and system sizes. We present here a series of numerical simulation studies of simple theoretical models, such as ballistic deposition model and biased solid-on-solid model, to demonstrate the dynamical scaling and phase transitions in a class of surface growth problems in the context of the Kardar-Parisi-Zhang theory. Different dynamical processes, such as desorption and surface diffusion, are shown to have dramatic effects on the scaling and thus the surface structures.

Externally applied electric fields are widely employed during thin-film deposition to improve film uniformity, texture and densification. Despite extensive experimental evidence, the physical mechanisms by which such fields influence nucleation, surface diffusion, island coalescence and interface stability remain theoretically fragmented. Classical thin-film growth models assume a field-free energetic landscape and therefore provide limited predictive guidance for field-assisted manufacturing strategies. In this work, we introduce the Field-Driven Growth Model (FDGM), a unified theoretical framework that incorporates field-matter interactions directly into the free-energy functional governing thin-film growth. By explicitly accounting for effective dipolar coupling arising from field-induced polarization of surface species, predominantly quadratic in the field amplitude and consistent with linear-response polarization, the model consistently modifies the fundamental processes of nucleation, surface diffusion and coalescence. At the continuum scale, the FDGM predicts a field-induced stabilization mechanism that suppresses long-wavelength roughening modes and defines a field-controlled morphological crossover wavelength (field-controlled cutoff). The FDGM demonstrates that field-assisted nucleation bias, anisotropic surface diffusion, field-biased coalescence pathways and morphological stabilization are not independent phenomena, but multiscale manifestations of a single energy-minimization principle acting on a field-modified energy landscape. By providing analytical stability criteria and explicit links between external field parameters and morphological outcomes, the model establishes a predictive foundation for the manufacturing of thin films with improved uniformity in advanced thin-film-based devices. The framework is broadly applicable to deposition techniques such as sputtering, pulsed-laser deposition, chemical vapor deposition and atomic layer deposition.

A ballistic deposition model for films evaporated over topography

We study a ballistic deposition model in 1+1 dimensions in which the incident angles (the angles between the incident trajectories and the substrate) of incoming particles are randomly distributed in the range [θ,π-θ]. We find a sharp morphological transition at a critical angle θ c ≃10 o . For θ>θ c , the scaling properties of the interface are described by the Kardar-Parisi-Zhang equation. For θ<θ c , the shadowing effect leads to a very different morphology. We determine the scaling properties of this new universality class numerically and analytically

Scaling properties of surface growth on rough substrates generated by standard models

We present simple computer algorithms able to build random packings of spheres using the ballistic deposition model and we show how they can be used to investigate several size segregation phenomena occuring in granular systems: 1) penetration of a small sphere in a packing of large ones, 2) size-segregation in the formation of a heap or when pouring a silo, 3) size-segregation by shaking. In the last case, the computer simulation provides a very simple geometrical explanation of the phenomenon

Geometrical properties of a random packing of hard spheres

Several studies, both theoretical and experimental, show that sedimentary rocks have a fractal pore-grain interface. In this paper a computer simulated 3-D sedimentary rock structure generated by the Relaxed Ballistic Bidisperse Deposition Model (RBBDM), is investigated to characterize the micro structure of its pores. The pore volume and the rock-pore interface show the same fractal dimension indicating that the pore volume is a fractal. The two point density correlation is computed for the pore space and the results compare favourably with the range reported from experiments. An array of 2-D X-ray tomography micrograph sections of a real sedimentary rock, an oolitic limestone (pure calcite) from the Mondeville formation of Middle Jurassic age (Paris Basin, France), was used to generate a 3-D bitmap. The 3-D real rock sample generated in this manner, was analysed for similar studies as the simulated structure. The results were compared with those obtained from simulation. The simulation results agree qualitatively with the real rock sample. Diffusion through the connected pore space of the simulated structure was studied using a random walk algorithm and the results compared with the similar simulation study done on the 3-D oolitic limestone specimen. In both cases diffusion was found to be anomalous indicating that the sedimentary rock has a fractal geometry. The favourable comparability of results between the simulated and real rock supports the usefulness of the model of sedimentary rock generation which can be applicable to transport phenomena.

We report pattern formation using a slippery ballistic deposition (SBD) model where growth germinates from a single site or from sites distributed periodically on a lattice. By changing the sticking probability p(s) and choosing systems with different lattice constants and symmetries, we demonstrate that a variety of patterns can be generated. These patterns can be further used as scaffolds for nanofabrication. We also demonstrate that by choosing a lateral sticking probability p(l) at the base that is different than p(s), one can control both the early and late time morphologies originating from a seed. Furthermore, we indicate a possible generalization of preparing patterns to higher dimensions that in principle can have potential technological applications for preparing grooves and scaffolds of specific shapes and periodicities.

The growth of self-affine fractal surfaces

Iridium (Ir) thin films have been extensively investigated for a variety of applications. Ir is a potential optical material for Fresnel zone X-ray microchannel plates, and inductive grid filters. It is also a noble metal making it well suited to corrosion resistance in harsh environments Atomic Layer Deposition (ALD) is considered a special case of chemical vapor deposition (CVD) in that two different chemical precursor materials are alternately introduced into a vacuum chamber where a chemical reaction occurs on the surface of the substrate. This method of thin film growth is self-limiting and conformal and consequently results in precise layer thickness control, stoichiometry, composition, and uniformity across a large surface area. Advantages that are unique to ALD include the ability to grow conformal thin films across complex geometries, and the relatively low temperatures required to achieve film growth. In this work, iridium metal films were synthesized on silicon (Si) and Monel K-500 alloy substrates by ALD using Iridium (III) acetylacetonate known as Ir(acac)3 or [CH3COCH=C(O-)CH3]3 Ir as precursor 1, and industrial grade O2 as oxidizing reactant. The solid Ir precursor was heated to 150 °C, and the substrate temperature was varied to establish an optimum growth window. The lowest temperature in which Ir growth was found is 200 °C, and the thin film growth rate increased as a function of temperature up to 250 °C. Higher temperatures have not yet been attempted due to equipment constraints. The Monel K-500 steel alloy flat discs were cut from commercially available Monel K-500 bars of ~1 inch diameter. In this study we report on the successful synthesis of Ir films on Si and Monel K-500 substrates. Detailed characterization has been performed using X-ray diffraction (XRD) techniques, atomic force microscopy (AFM), and field emission scanning electron microscopy (FE-SEM) of samples which have been notched with focused ion beam (FIB) techniques for cross-sectional film thickness measurements as revealed in Figure 1. The polycrystalline ALD Iridium film exhibited good chemisorption and adhesion to native oxide covered Si substrates, with hydroxyl surface termination. However even with the absence of a SiO2 surface film, the ALD synthesis of Iridium metal films worked equally well on the Monel K-500 steel alloy flat disc substrates and yielded excellent surface coverage.

Synthesis, electrical and ultrafast nonlinear optical properties of Sn–ZnO composite film

A numerical study on the effect of mobilities and initial profile in thin film morphology evolution

At present, computer simulation has become an important researching tool for thin film growth as one of theory method, which can be used to understand the mechanism of thin film growth at atom level. Now, most of simulations about thin film growth are about two dimensional and the object of simulation is only one kind of atom, such as Cu, Al, or Si on different substrate, and the work about simulation of oxide thin film growth is much less. However, many oxide thin films are playing very important role in electronic application because of their unique properties as functional materials, so it need to better understand the growth kinetics of oxide thin films. A new model for simulation of the growth of PbTiO/sub 3/ (abbreviated as PTO) thin film basing on kinetic Monte Carlo method has been developed in this paper. A pack of simulation software for PTO was developed. From the simulation it is obtained that the deposition rate and the substrate temperature play a very important role in the initial process of growth of PTO thin film, and with the rising of the substrate temperature and the decreasing of deposition rate, the size of the initial nucleuses gets larger and the number of them in unit area gets less. And with advance of modern instrument, it's possible to get the morphology of ABO/sub 3/ structure thin films at its initial stage of growth by STM to test and improve our model. The related experimental work is at hands.

Atom correlation and configurational ordering in pseudobinary epitaxial semiconductors