original_query: What is atomic layer deposition (ALD) and how does it differ from chemical vapor deposition?
query: What is atomic layer deposition (ALD) and how does it differ from chemical vapor deposition?
answer: Atomic layer deposition (ALD) is a thin-film deposition technique using sequential gas-phase chemical reactions.  Unlike chemical vapor deposition (CVD), where precursors are present simultaneously, ALD introduces precursors in non-overlapping pulses.  In ALD, each precursor reacts in a self-limiting way, stopping once all reactive surface sites are consumed. This allows for precise control over film thickness and uniformity.