Mar 24 th, 2016 Inorganic Material Chemistry

Gas phase physical deposition 1.Sputtering deposition 2.Evaporation 3.Plasma deposition

1. Sputtering deposition ■ Principle & Process - High-power laser beam strikes a target, and then vaporized target (ablation plume) deposits onto substrate as thin film (Sputtering) ■ Usages & Applications -Thin film of complex compounds with complicated stoichiometry (YBCO, ceramics, etc.) ■ Characteristics Advantages -Stoichiometry of a target can be reproduced on substrate (deposits almost any materials) Drawbacks - Requires ultra high vacuum -Possibility of incorporating impurities -Uneven coverage (Line-of-sight). Ag nanoparticles deposited on substrate Y 2 O 3 doped ZrO 2

2. Evaporation ■ Principle & Process - Solid metal source is thermally evaporated into vapor, and it deposits on the substrate. ■ Usages & Applications - Wide variety of thin films (semiconductors, metals, solar cells, etc.) ■ Characteristics Advantages -Deposits almost any materials -Low contamination Drawbacks -Undesired polycrystalline layers -Difficult to evaporate materials with low vapor pressure or high melting point. Thermally deposited metallic NPs

■ Principle & Process - Discharge electrode excites the reactant gas into a plasma, charged ions strikes target on the cathode, and then vaporized target (ablation plume) deposits onto substrate as thin film (sputtering). ■ Usages & Applications -Thin film of complex compounds with complicated stoichiometry (TiN, TiAlN, CrN, ZrN, AlCrTiN, TiAlSiN.) ■ Characteristics -Deposits almost any materials (metallic, ceramic) 3. Plasma deposition TiAlSiN Precursor: Pure metals (Cr, Ti) and AlSi alloy Rh nanoparticles Precursor: Pure Rh metal

Chemical vapor deposition (CVD) 1.Thermal enhanced CVD 2.Laser enhanced CVD 3.Plasma enhanced CVD 4.Chemical beam epitaxy

1. Thermal CVD ■ Principle & Process - Heat energy is supplied to activate required source and gas-solid phase reaction. ■ Usages & Applications - Thin films (Metal oxide, metal sulfide, silicon, various semiconductors, etc.) ■ Characteristics Advantages -High quality product -Simple reactor -Large-scale synthesis Drawbacks -Large quantity carrier gas in need -Hard to detach the product from substrate Graphene Precursor: CH 4 + H 2 Gas

2. Laser-assisted CVD ■ Principle & Process - Chemical reaction of source gas takes place at the spot on the substrate under laser irradiation. ■ Usages & Applications - Thin rod and fibers. (Si, C, B, Al, etc.) ■ Characteristics - Control of directionality Carbon nanotube Precursor: C 2 H 4 Catalyst: FePrecursor: SiH 4 Silicon wire

3. Plasma enhanced CVD ■ Principle & Process - Discharge electrode excites the reactant gas into a plasma (ionized gas), which induces a chemical reaction and results in the reaction product being deposited on the substrate. ■ Usages & Applications - High quality silicon complex thin film (SiO x, SiN x, amorphous silicon, dopant) ■ Characteristics Advantages: -Lower temperature( °C) processes compared to conventional CVD (Less damages to sample, good when temperature is restricted) -Fast deposition -High step coverage (High quality) Drawbacks -Toxic byproduct gas -High cost Silicon nanoparticles Precursor: SiH 4 Deposition of SiO 2 Precursor: SiH 4, N 2 O, N 2

4. Chemical beam epitaxy ■ Principle & Process -Reactants are molecular beam of reactive gases, typically as hydride or metalorganic. -Molecular beam (alkyl beam) carries metal atoms. Decomposition happens on the substrate for metal to compose layered structure on the substrate. ■ Usages & Applications -Semiconductor films (GaAs, InP, Si 1-x Ge x, etc.) -Heterostructures (GaAs/InGaAs films) -Carbon doped semiconductors (p-type GaAs) ■ Characteristics Advantages -Low growth temperature -Uniform film coverage Drawbacks -Requires ultra high vacuum ( ~ ) -High carbon contamination Precursor: AsH 3, (C 2 H 5 ) 3 Ga