| 摘要 |
Gas flow from multiple gas sources into a sample chamber of a beam system is controlled by a cycling valve for each gas source, with the gas pressure in the sample chamber being determined by the relative time that the valve is opened and the upstream pressure at the valve. A gas valve positioned inside the vacuum chamber allows rapid response in shutting off a gas. In some preferred embodiments, a precursor gas is supplied from a solid or liquid material in a container that remains outside the vacuum system while in use and which is readily connected or disconnected to the gas injection system without significant leakage.
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