Chemical Synthesis Techniques Chemical Synthesis Techniques - - PowerPoint PPT Presentation

Chemical Synthesis Techniques Chemical Synthesis Techniques Chemical Synthesis Techniques Chemical Synthesis Techniques

Thin Films & Variations

Electrochemical Deposition Electrochemical Deposition

(Electrodeposition, Electroplating) (Electrodeposition, Electroplating)

V

Deposition of materials from an electrolyte by the passage of an

f

• +

electrolyte by the passage of an electrical current.

Reference Electrode Working Electrode

• +

Counter Electrode

n

M  M

n  ne

M

n  ne  M.

Electrolyte

M  M  ne

Liu, UCD Phy250-1, 2011, NanoFab

Electrodes Electrodes

Counter electrode: conducting & stable e.g., Pt Working electrode: conducting & stable also substrate for deposition also substrate for deposition Reference electrode: compatible w/ electrolyte

H2 Ag Ag+/AgCl SCE Pt Hg/HgSO4

2

g g g

4

Potential (mV) 110 100 30 330 80

Liu, UCD Phy250-1, 2011, NanoFab

Deposition Process Deposition Process

M  M

n 

Immersing metal electrode into a solution

M  M  ne M

n  ne  M.

M  ne  M.

Equilibrium potential of the metal - ion pair: Nernst equation

E E  (RT/ F)l ( / ) Eeq  Eo  (RT/ nF)ln(a/ am),

R =8.314 J/K mole, F is the Faraday constant (96,500 C/mole), n is the valence, a and am are the activities of the ion and metal

  Eappl  Eeq

Over-potential l i d i l d i i l

Liu, UCD Phy250-1, 2011, NanoFab

For metal ion reduction to metal: need negative over-potential

Varibles Varibles

Potential-pH phase diagram: Pourbaix diagram Current efficiency CE

% 100 /  

Faraday a W

W CE

Liu, UCD Phy250-1, 2011, NanoFab

Monitoring charge transfer to control growth

Types of Electrodeposition Types of Electrodeposition

Single bath DC Pulse Dual bath Dual bath Advantages: Ambient T & P Cost effective Deposition onto complex structures

Liu, UCD Phy250-1, 2011, NanoFab

Multilayer Deposition Multilayer Deposition

tial l

Cu Co Open Circuit Co Open Circuit

pplied Potentia vs Ag+/AgCl

VCu= -0.16V

5 10 cm

2)

Co dissolution Cu dissolution

Ap v

VCo= -1.00V

ent

5 rrent density (mA/c Cu deposition

position current

ICu I = 0 ICu

• 10
• 5
• 1.0
• 0.8
• 0.6
• 0.4
• 0.2

0.0 0.2 Cur A li d t ti l (V) Co deposition

Depos

ICo

Applied potential (V)

Liu, UCD Phy250-1, 2011, NanoFab Time (s)

Multilayered Nanowires Multilayered Nanowires

Liu, UCD Phy250-1, 2011, NanoFab

CVD CVD

Liu, UCD Phy250-1, 2011, NanoFab