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Author: Ali Kosari Mehr
Laser chemical vapor deposition (LCVD) is a modified CVD process for the deposition of thin films. An LCVD device is comprised of a chamber having inlets for reagent gases. Accordingly, heated by a focused laser beam, reagent gases can decompose to form metallic or ceramic films. Equipped with a local laser heating system, an LCVD device can enable patterning and writing through the movement of the focused laser beam relative to the substrate. Mainly, two reagent gases are introduced into the chamber, culminating in a thin solid film and a by-product at the end of the process.
In general, an LCVD process is classified into two subcategories:
1- Photolytic LCVD: In this process, the energy of the focused laser beam is absorbed by reagent gases, leading to the decomposition of gas molecules and the formation of a thin solid film on the substrate. Moreover, laser wavelengths should be deliberately selected to be dependent on the materials due to the fact that the energy is absorbed by gas molecules in the photolytic LCVD process. Typically, ultraviolet lasers such as KrF, Ar+, and ArF are utilized in the process.
2- Pyrolytic LCVD: In this process, the laser beam is focused on the locations to be deposited. Thus, the temperature locally increases on the substrate until it reaches a threshold required, hence resulting in the deposition of a thin solid film on the substrate. Typically, continuous-wave infrared lasers such as Nd:YAG and CO2 are utilized in the process.
In lieu of the confinement of the laser absorption in the beam focal point, the laser absorption might extend along the laser beam in the photolytic LCVD process, causing a decrease in resolution and an increase in thickness and width. Nonetheless, as being more localized, the heating in the pyrolytic LCVD process allows better resolution (up to 5 μm).
References:
1. Alemohammad H, Toyserkani E (2010) Laser-assisted additive fabrication of micro-sized coatings. In: Advances in Laser Materials Processing: Technology, Research and Application. Elsevier Inc., pp 735–762 Webpage
2. Wasa K, Kitabatake M, Adachi H (2004) Thin Films Material Technology: Sputtering of Compound Materials. Springer. Webpage
