Y. Liou

The effect of oxygen in diamond deposition by microwave plasma enhanced chemical vapor deposition

High quality diamond thin films were deposited on different substrates at temperatures from 300 to 1000 °C by the microwave plasma enhanced chemical vapor deposition (MPCVD) system. The quality of deposited diamond films was improved by adding oxygen in the gas mixtures. Different ratios of methane to oxygen concentration in hydrogen at different temperatures have been studied. At high temperatures (800–1000 °C), the addition of oxygen will not only enhance the growth rate of deposited films but also extend the region of diamond formation. At low temperatures ( 900 °C) were either graphitic or diamond containing a large amount of graphitic or amorphous carbon and at low temperatures (

Effect of oxygen in diamond deposition at low substrate temperatures

Thin diamond films were deposited on different substrates at temperatures below 500 °C by a microwave plasma‐enhanced chemical vapor deposition system. The deposited films were amorphous carbon or diamond films depending on the different gas mixtures used. The addition of oxygen to the gas mixtures was found to be critical for diamond growth at low temperatures. Without oxygen, the deposited films were white soots and easily scratched off. Increasing the oxygen input improved the quality of the Raman peaks and increased the film transparency. The diamond films were also characterized by scanning electron microscopy.

Real-time and spectroscopic ellipsometry characterizatio of diamond and diamond-like carbon

Abstract Recent advances in real-time and spectroscopic ellipsometry characterization of vapor-deposited thin film diamond, diamond-like carbon, and their synthesis are reviewed. Examples are presented in which ellipsometric techniques have led to insights into growth mechanisms and film structure that would have been difficult to elicit by other methods. The determination of the bulk and interface optical properties of diamond-like films in real time and the application of the techniques to obtain reproducibly tailored interfaces are demonstrated. Real-time ellipsometry has also been used to survey preparation parameter space and establish conditions that lead to sustained film growth or etching. Spectroscopic measurements of the surface, bulk, and interface structure of assisted chemical vapor deposited diamond films will also be discussed. Ellipsometry coupled with preferential chemical etching can determine the thickness and evolution of carbide layers formed on the substrate before diamond nucleation. For microwave plasma deposition of diamond on c-Si at 980°C, the SiC is 40 to 70 A and is present on all Si substrates studied.

Methods for a precision measurement of ionic masses and appearance energies using the pulsed‐laser time‐of‐flight atom probe

An attempt has been made to use the pulsed‐laser time‐of‐flight atom probe for a precision measurement of ionic masses and the critical energy deficits, or the appearance energies, of field emitted ions. For this purpose methods for determining accurately the flight‐path constant and the time‐delay constant of the atom probe have been devised. Using 300‐ps laser pulses and a digital electronic timer of 1‐ns resolution and a flight path of slightly over 4 m, ionic masses of pulsed‐laser field desorbed gaseous ions can be measured with an accuracy of better than 0.0005 to 0.003 amu for ions of low to intermediate masses. For multiply charged field evaporated heavy metal ions, the accuracy is not as good due mainly to the very limited number of ions which can be collected at a given low emitter voltage. The accuracy of measuring the critical energy deficit depends on the emitter voltage, and the mass and the charge of the ions. It ranges from ∼0.3 eV for singly charged, heavy gas ions at a low emitter voltag...

Low Temperature Diamond Deposition On Glass

Diamond films by chemical vapor deposition have good potential for optical application only if transparent films can be produced. Thin diamond films were deposited on silicon, lead glass, MgO, fused silica and soda-lime silica at low temperatures (<500°C) by microwave plasma enhanced chemical vapor deposition. Low temperatures were achieved either by lowering microwave powers and pressures or by remoting the plasma. The deposited films were either white and transluscent or highly transparent depending on the different gas mixtures being used. The effect of gas composition on diamond formation will be discussed. Raman peak shifts of 2 to 8 cm-1 were observed due to the strain in the film. The exact temperature of the growth surface is uncertain as measurements were made only of the substrate bulk. Estimated temperatures were reported by careful calibration.

Surface analysis with pulsed‐laser stimulated field desorption

Using a pulsed‐laser stimulated field desorption time‐of‐flight spectrometer, known as the pulsed‐laser atom probe, surface atoms and atomic layers of one’s choice can be mass analyzed one by one. In addition, it is an ion kinetic energy analyzer with which the binding energy of surface atoms can be measured. We have developed a high‐resolution system which measures flight time of each ion with a time resolution of 156 ps. With a flight path of ∼778 cm, this system has a resolution and accuracy of about one to two parts in 105 in mass analysis, ion kinetic energy analysis, and ion reaction rate measurement. This system has been used to study the binding energy of surface atoms in well‐defined sites, formation of cluster ions and their magic and critical numbers, compositional variation across the interface of silicon and silicide layer, field induced surface states, field dissociation of compound ions, and other desorption phenomena. We describe here this high‐resolution system, how it is calibrated, and ...

A PRECISION MEASUREMENT OF ABSOLUTE IONIC MASSES AND ENERGIES OF FIELD EMITTED IONS

Methods have been devised to measure the absolute mass and energy of field emitted ions to an accuracy better than 0.0005 amu and 0.5 eV using the pulsed-laser time-of-flight atom-probe.