L11-Thin_Film_Growth

L11-Thin_Film_Growth - Thin Film Growth and Evolution Thin...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
Thin Film Growth and Evolution
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Thin Film Techniques
Background image of page 2
Steps of Thin Film Growth 1. Absorption (physisorption) 2. Surface diffusion 3. Chemical bond formation (chemisorption) Molecule-molecule Substrate-molecule 4. Nucleation 5. Microstructure formation Crystal structure Defects 6. Bulk changes Diffusion Grain growth 1 2 3 4 5 6
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Physisorption An approaching atom can either be reflected or absorbed on to the surface of the substrate. The process is dependent on the incoming flux of atoms the trapping probability the sticking coefficient
Background image of page 4
Energy Barriers Once physisorbed, the atom can be chemisorbed or desorbed (ejected). Both physisorption and chemisorption have to overcome local energy barriers. ¸ ¹ · ¨ © § ± kT E vk b r exp ¸ ¹ · ¨ © § kT E b r r exp 11 W E a E P E C r C r P Distance From Surface Potential Energy E P ~ 0.25 eV E C ~ 1 - 10 eV
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Adsorption Effects Whether physical or chemical, adsorption is counterbalanced by desorption. If P is the partial pressure of the atoms in the vapor phase and k ads and k des the adsorption and desorption rates, then the surface coverage percentage, T , as a function of time is, If KP >> 1 then coverage is unity. At very long times, the equilibrium coverage is, ±² >@ ^` t KP k KP KP des ³´ ´ ³ 1 exp 1 1 des ads k k K KP KP ³ 1
Background image of page 6
Surface Energy Once an atom sticks to the surface, it creates a tension (energy) in the surface. It is due to the surface atoms stretching their bonds in response to the absorption of the atom. It is a function of the broken bond energy of exposed surface atoms which depends on the crystal structure of the substrate.
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Surface Diffusion Overall surface energy can be minimized if the atom has enough energy and time to diffuse to a low energy site.
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 26

L11-Thin_Film_Growth - Thin Film Growth and Evolution Thin...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online