Effects of hydrogen impurities on the diffusion, nucleation, and growth of Si on Si(001)

Silicon epitaxy on H-terminated Si (100) surfaces at 250 °C

Low temperature Si epitaxy has become increasingly important due to its critical role in the encapsulation and performance of buried nanoscale dopant devices. We demonstrate epitaxial growth up to nominally 25 nm, at 250°C, with analysis at successive growth steps using STM and cross section TEM to reveal the nature and quality of the epitaxial growth. STM images indicate that growth morphology of both Si on Si and Si on H-terminated Si (H: Si) is epitaxial in nature at temperatures as low as 250 °C. For Si on Si growth at 250 °C, we show that the Si epitaxial growth front maintains a constant morphology after reaching a specific thickness threshold. Although the in-plane mobility of silicon is affected on the H: Si surface due to the presence of H atoms during initial sub-monolayer growth, STM images reveal long range order and demonstrate that growth proceeds by epitaxial island growth albeit with noticeable surface roughening.

Influences of h on the adsorption of a single ag atom on si(111)-7 × 7 surface

The adsorption of a single Ag atom on both clear Si(111)-7 × 7 and 19 hydrogen terminated Si(111)-7 × 7 (hereafter referred as 19H-Si(111)-7 × 7) surfaces has been investigated using first-principles calculations. The results indicated that the pre-adsorbed H on Si surface altered the surface electronic properties of Si and influenced the adsorption properties of Ag atom on the H terminated Si surface (e.g., adsorption site and bonding properties). Difference charge density data indicated that covalent bond is formed between adsorbed Ag and H atoms on 19H-Si(111)-7 × 7 surface, which increases the adsorption energy of Ag atom on Si surface.

Vacancy dynamics and reorganization on bromine-etched Si(100)-(2 x 1) surfaces

Halogen etching of Si(100) surfaces has long been considered to involve the selective removal of atoms from an essentially static surface. Here we show that vacancy sites produced by etching are mobile at elevated temperature and rearrange to form features that were considered to be the direct products of etching. We demonstrate that the etch features observed at different temperatures are not due to different mechanisms. Rather, kinetic etch products formed at low temperatures are transformed into thermodynamically more stable features at higher temperatures.

Interaction of H2 with Si(001)-(2 x 1): solution of the barrier puzzle

The sticking probability of H2 on Si(001) is immeasurably small at room temperature, indicating the presence of a large energy barrier to adsorption. Surprisingly, the final state energy distributions of H2 molecules desorbing from Si(001) show no signs of having traversed such a barrier, in apparent contradiction with microscopic reversibility. Here we report experimental and theoretical evidence resolving this long-standing puzzle. Adsorption and desorption proceeding along two distinct, microscopically reversible pathways can explain all observations.

AN ATOMISTIC VIEW OF Si(001) HOMOEPITAXY

▪ Abstract  Growth of thin films from atoms deposited from the gas phase is intrinsically a non-equilibrium phenomenon dictated by a competition between kinetics and thermodynamics. Precise control of the growth becomes possible only after achieving an understanding of this competition. In this review, we present an atomistic view of the various kinetic aspects in a model system, the epitaxy of Si on Si(001), as revealed by scanning tunneling microscopy and total-energy calculations. Fundamentally important issues investigated include adsorption dynamics and energetics, adatom diffusion, nucleation, sticking, and detachment. We also briefly discuss the inverse process of growth, removal by sputtering or etching. We aim our discussions to an understanding at a quantitative level whenever possible.

Atomistic Processes in the Early Stages of Thin-Film Growth

Growth of thin films from atoms deposited from the gas phase is intrinsically a nonequilibrium phenomenon governed by a competition between kinetics and thermodynamics. Precise control of the growth and thus of the properties of deposited films becomes possible only after an understanding of this competition is achieved. Here, the atomic nature of the most important kinetic mechanisms of film growth is explored. These mechanisms include adatom diffusion on terraces, along steps, and around island corners; nucleation and dynamics of the stable nucleus; atom attachment to and detachment from terraces and islands; and interlayer mass transport. Ways to manipulate the growth kinetics in order to select a desired growth mode are briefly addressed.