Laser-enhanced CVD

LECVD Laser-enhanced CVD PLD Pulsed-laser deposition... 

LECVD (laser-enhanced CVD) uses a laser beam to enhance reactions at the substrate surface. One feature of this technique is that it is possible to write materials on the substrate the deposit is formed only where the scanned light beam hits the substrate. 

Laser-enhanced CVD Increasing the reaction rate using a laser to provide thermal energy by the adsorption of radiation by the substrate or by photodecomposition of the chemical vapor precursor. 

There are numerous materials, both metallic and ceramic, that are produced via CVD processes, including some exciting new applications such as CVD diamond, but they all involve deposition on some substrate, making them fundamentally composite materials. There are equally numerous modifications to the basic CVD processes, leading to such exotic-sounding processes as vapor-phase epitaxy (VPE), atomic-layer epitaxy (ALE), chemical-beam epitaxy (CBE), plasma-enhanced CVD (PECVD), laser-assisted CVD (LACVD), and metal-organic compound CVD (MOCVD). We will discuss the specifics of CVD processing equipment and more CVD materials in Chapter 7. 

A variety of CVD methods and CVD reactors have been developed, depending on the types of precursors used, the deposition conditions applied, and the forms of energy introduced to the system to activate the chemical reactions desired for the deposition of solid fihns on snbstrates. For example, when metalorganic compounds are used as precursors, the process is generally referred to as MOCVD (metalorganic CVD), and when plasma is nsed to promote chemical reactions, this is called plasma-enhanced CVD (PECVD). There are many other modified CVD methods, such as LPCVD (low-pressure CVD), laser-enhanced or assisted CVD, and aerosol-assisted CVD (AACVD). 

These specialized forms of CVD, referred to as nontraditional techniques for the purpose of this review, include laser (LCVD), aerosol (ACVD), hot filament (HFCVD), and ion beam (IBGVD) chemical vapor deposition. In such enhanced CVD technologies, a thermal CVD reaction occurs simultaneously with another driving force, which results... 

Tremendous fundamental research especially in the CVD technologies and precursor synthesis extends the applicability to some new area. These technologies include metal-organic CVD (MOCVD), plasma-enhanced CVD, photo CVD and laser induced CVD etc. The advancement of the synthesis technology provides new precursors to deposit a variety of materials with high purity. 

CVD can also be classified using its activation methods. Thermal activated CVD processes are initiated only with the thermal energy of resistance heating, RF heating or by infrared radiation. They are widely used to manufacture the materials for high-temperature and hard-to-wear applications. In some cases enhanced CVD methods are employed, which includes plasma-enhanced CVD (PECVD), laser-induced CVD (LCVD), photo CVD (PCVD), catalysis-assisted CVD and so on. In a plasma-enhanced CVD process the plasma is used to activate the precursor gas, which significantly decreases the deposition temperature. 

In the Chemical Vapor Deposition (CVD) methods, the starting material undergoes specific chemical reactions at the hot surface of the substrate to form thin layers of the desired material. The reaction can be stimulated by various energy sources, e.g. plasma, giving plasma enhanced CVD (PECVD), or a laser, giving laser CVD. 

In the first chapter of this book, an overview of CVD techniques has been given, and more detailed descriptions can be found in several textbooks [9, 10]. Many different CVD reactors have been used for the deposition of conducting films, i.e., thermal, UV-enhanced CVD (UVCVD), laser-assisted CVD (LACVD), plasma-enhanced CVD (PECVD) and metal-organic CVD (MOCVD). In addition, two techniques were included, which are not typically part of CVD, chemical transport and spray pyrolysis. 

Nanoparticles can be produced by several methods including mechanical, electric arc discharge, laser ablation, chemical vapor deposition (CVD), plasma-enhanced CVD (PECVD) and wet chemical reactions. 

An extensive method which also shows multivariable process can adjust in a several manner like plasma enhanced CVD, thermochemical CVD, aerogel supported, high pressure CO disproportionation, alcohol catalytic CVD, aerosol assisted CVD, and hybrid laser assisted thermal CVD... 

Plasma-enhanced CVD is a modified CVD method. Source materials are fully reacted in the plasma region and are then deposited on the heated substrate in crystalline form to prepare thin films of oxides. High vacuum is not required, so that an inexpensive vacuum device can be used. The deposition rate is high, and the process is cheap. It is a favorable choice for mass production. Similar to pulse laser deposition, the thickness of the prepared films is in the nanometer range, and their electrochemical performance is good. For example, the prepared amorphous LiMn204 thin film exhibits a specific capacity of 39 iAh/(cm2 pm). After 700 cycles, its capacity fading rate is only 0.04%/cycle. 

An example of this process is laser-induced CVD, where the radiation frequency is tuned to the vibrational frequency of the precursor molecule, to enhance decomposition. This resonance absorption/excitation is the basis of laser-induced fluorescence, which may be used to determine species on a surface or in the gas phase. 

DEC coating was first prepared by Aisenberg and Chabot using ion beam deposition in 1971 [2]. At present, PVD, such as ion beam deposition, sputtering deposition, cathodic vacuum arc deposition, pulsed laser deposition, and CVD, like plasma enhanced chemical vapor deposition are the most popular methods to be selected to fabricate DEC coatings. 

The preparation of CNTs is a prerequisite step for the further study and application of CNTs. Considerable efforts have been made to synthesize high quality CNTs since then-discovery in 1991. Numerous methods have been developed for the preparation of CNTs such as arc discharge, laser vaporization, pyrolysis, and plasma-enhanced or thermal chemical vapor deposition (CVD). Among these methods, arc discharge, laser vaporization, and chemical vapor deposition are the main techniques used to produce CNTs. 

---