Hyeongtag Jeon

Morphology and phase stability of TiSi2 on Si

The formation mechanisms and properties of TiSi2 on Si are investigated. The particular emphasis is in relating the nucleation, morphology, and phase stability of the films. TiSi2 films were prepared by deposition of Ti on atomically clean silicon substrates in ultrahigh vacuum. The silicide formation was initiated either by in situ annealing or deposition onto heated substrates. The island formation of TiSi2 and surface and interface morphologies of TiSi2 were examined by scanning electron microscopy and transmission electron microscopy. The TiSi2 formation process was monitored with in situ Auger electron spectroscopy and low‐energy electron diffraction to analyze the surface concentration and the surface structures, respectively. Raman spectroscopy was used for phase identification of the TiSi2. Titanium film thicknesses from 50 to 400 A were examined. For all thicknesses studied, the C49 TiSi2 phase is observed to nucleate. Immediately after low‐temperature deposition, the interface morphology was smo...

Raman scattering characterization of titanium silicide formation

Raman scattering is used to probe the reactions at the interface of Ti and Si. Different titanium-silicide and titanium-oxide spectral signatures which can be used to characterize the thin-film are observed. In addition, the Raman spectrum of metallic Ti deposited on Si is detected and is used to monitor the Si interdiffusion. The 40-nm-thick Ti films were evaporated in UHV or high-vacuum environments, and in situ Raman measurements of the Ti film and the Si substrate are tracked as a function of vacuum annealing at temperatures up to 500 degrees C. The results show that extensive Si interdiffusion into the Ti occurs between 300 and 400 degrees C and that the interdiffusion precedes silicide compound formation. The TiSi/sub 2/ formation is discussed in terms of a nucleation model. The silicide formation temperature is related to the nucleation barrier, and it is proposed that impurities increase the nucleation barrier, which results in the observed higher silicide formation temperature. >

Surface morphology of TiSi2 on silicon

Abstract The formation mechanisms and morphology of TiSi 2 on silicon are explored. TiSi 2 is formed on atomically clean Si(100) and Si(111) substrates by UHV deposition of titanium and in situ annealing. The TiSi 2 formation process is monitored with in situ low energy electron diffraction and Auger electron spectroscopy, and the morphology is examined with ex situ scanning electron microscopy. Titanium thickness between 50 and 400 A were examined. The TiSi 2 formation process involves interdiffusion at temperatures less than 400°C, formation of a metastable TiSi 2 phase at about 500°C, and transformation to the stable TiSi 2 phase at about 700°C. The results show TiSi 2 island formation after annealing at between 700 and 900°C, depending on the film thickness. The low energy electron diffraction measurements showed that the exposed silicon regions exhibited reconstructed surface structures after the island formation. The island formation process is described in terms of a wetting model, and the surface energies for nucleation and island formation are related.

Surface electronic states of low-temperature H-plasma cleaned Si(100)

The surface of low‐temperature H‐plasma cleaned Si(100) was studied by angle‐resolved UV photoemission spectroscopy. The cleaning process involved an ex situ wet chemical preclean followed by an in situ H‐plasma exposure at a substrate temperature of 300 °C. After the in situ H‐plasma exposure, a 2×1 ordered surface was obtained which exhibited two hydrogen‐induced surface states/resonances in the UV photoemission spectra. The temperature dependence of the spectra showed that the Si‐H monohydride started to dissociate at a temperature below 500 °C, and the dangling‐bond surface states were identified. The spectroscopic properties of the low‐temperature H‐plasma surface were essentially identical to surfaces prepared by ultrahigh vacuum high‐temperature annealing followed by H passivation.

Interface Morphology, Nucleation and Island Formation of Tisi 2 on Si(111).

In this study we investigate the formation mechanisms and morphology of TiSi 2 formed by deposition of Ti on atomically clean silicon substrates. Ti films of 50–400 A thickness were deposited in ultra-high vacuum on Si (111) wafers and annealed to temperatures between 500–900°C. Films were monitored in situ with AES and LEED, and post preparation characterization was accomplished with SEM, TEM and Raman scattering. The results show that for films of thickness ≤, 100 A the C49 TiSi 2 phase is stable over the entire 600-800°C temperature range. However, for films of 200-400 A thickness, the C49 to C54 phase transition occurs at temperatures varying from 700 to 800°C dependent upon film thickness. The high temperature annealing results in flat interface structures, and island formation is observed for all films with the C54 structure. The interface morphology and the mechanisms of TiSi 2 island and phase formation are discussed in terms of surface and bulk free energies considerations based on nucleation theory.

Surface Morphologies and Interfaces of TiSi 2 Formed from UHV Deposited Ti on Si

The island formation of TiSi 2 and the surface morphologies and interfaces of TiSi 2 on Si have been examined and related to the surface and the interface energies. Ti (200A and 400A) films were deposited on clean, reconstructed Si(100) and Si(111) substrates at room temperature and also at high substrate temperatures (500°C~800°C). The TiSi 2 formation process is monitored with in-situ LEED and AES and the surface morphologies and interfaces are examined with ex-situ SEM and TEM. For annealing to temperatures such that the C54 phase forms, the results indicate island formation with clean reconstructed substrate regions between the islands. The TiSi 2 islands show different morphology on the (100) and (111) oriented substrates. The mechanism of TiSi 2 island formation is described in terms of a liquid-liquid model, and the surface and interface energies for the TiSi 2 island are determined from contact angle measurements.

Growth and Characterization of Heteroepitaxial Nickel Films on Diamond Substrates

In the present study epitaxial Ni(001) films have been grown on natural C(001) substrates (type la and Ha) and homoepitaxial C(001) films. Two deposition techniques including electron-beam evaporation of Ni in a molecular beam epitaxy (MBE) system and evaporation of Ni from a resistively heated tungsten filament have been employed. As evidenced by scanning electron microscopy (SEM), the Ni films deposited by electron-beam evaporation were found to replicate the very fine, unidirectional scratches present on the as polished C(001) substrates. Indeed, the coverage and uniformity of the deposited films would imply a two-dimensional (2-D) growth mode. In comparison, the thermal evaporation of Ni on C(001) substrates results in a highly textured and faceted surface morphology indicative of three-dimensional (3–D) nucleation and growth. Moreover, Rutherford backscattering/channeling measurements have demonstrated that the Ni(001) films deposited by electron-beam evaporation are of superior crystalline quality. Differences in the observed microstructure and apparent growth modes of the epitaxial Ni(001) films have been attributed to the presence of oxygen incorporation in those layers deposited by thermal evaporation.

X-Ray Absorption Studies of Titanium Silicide Formation at the Interface of Ti Deposited on Si

Near edge X-ray absorption spectra (XANES) have been obtained from the Ti K-edge for several series of titanium silicide samples produced by different techniques. Samples were fabricated by depositing Ti on silicon wafers and subsequently annealing them up to temperatures from 100°C to 900°C in UHV, vacuum furnace, or in a Rapid Thermal Annealing system. Measurements were done in the fluorescence and total electron yield modes. The XANES measurements were correlated with Raman scattering measurements. The XANES data of several reference compounds were obtained, and the data showed a high sensitivity to changes in the film structure. Ti metallic bonding and Ti-Si bonds can be distinguished and their evolution as a function of annealing is related to previous results. For the samples with increased impurities, Ti regions were stable at higher temperatures. The XANES spectra of samples annealed under N 2 indicate the formation of a surface nitride.

Characterization of Titanium Silicide Contacts Deposited on Semiconducting Diamond Substrates

Abstract The first results pertaining to the growth and characterization of titanium silicide contacts deposited on natural semiconducting diamond substrates are reported. The titanium silicide films were formed by the co-deposition of silicon and titanium in ultra-high vacuum by electron-beam evaporation in a molecular beam epitaxy (MBE) system. The grown layers have been characterized using Raman spectroscopy, scanning tunneling microscopy (STM) and current-voltage (I-V) techniques. In particular, it has been shown from I-V measurements taken at room temperature that the titanium silicide film forms a low-barrier rectifying contact. Consistent with the observed low-barrier height, the corresponding I-V measurements recorded at 400°C exhibit ohmic-like behavior. However, on subsequent annealing of the titanium silicide contacts at 1100°C, stable rectifying I-V characteristics were observed in the 25 -400°C temperature range.