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) Deposition of materials from an V electrolyte by the passage of an electrolyte by the passage of an electrical current. - - + + Reference f Counter Working Electrode Electrode Electrode n   ne  M . n  M n   ne M  M M  M  ne Electrolyte 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 Ag + /AgCl Pt Hg/HgSO 4 g g H 2 Ag g SCE 4 2 Potential 110 100 30 330 80 (mV) Liu, UCD Phy250-1, 2011, NanoFab

Deposition Process Deposition Process Immersing metal electrode into a solution n   M  M M  M  ne n   ne  M .  ne  M . M M Equilibrium potential of the metal - ion pair: Nernst equation E eq  E o  ( RT / nF )ln( a / a m ), E  ( RT / F )l ( / E ) R =8.314 J/K mole, F is the Faraday constant (96,500 C/mole), n is the valence, a and a m are the activities of the ion and metal   E appl  E eq Over-potential For metal ion reduction to metal: need negative over-potential l i d i l d i i l Liu, UCD Phy250-1, 2011, NanoFab

Varibles Varibles Potential-pH phase diagram: Pourbaix diagram Current efficiency CE   CE W a W / 100 % Faraday Monitoring charge transfer to control growth Liu, UCD Phy250-1, 2011, NanoFab

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 Co Open Open Cu Co Circuit Circuit tial pplied Potentia vs Ag+/AgCl l V Cu = -0.16V 10 Cu dissolution 2 ) Co dissolution 5 cm v Ap rrent density (mA/c V Co = -1.00V 0 Cu deposition ent position current Cur -5 5 I = 0 Co deposition I Cu I Cu -10 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 Depos A Applied potential (V) li d t ti l (V) I Co Time (s) Liu, UCD Phy250-1, 2011, NanoFab

Liu, UCD Phy250-1, 2011, NanoFab Multilayered Nanowires Multilayered Nanowires

Liu, UCD Phy250-1, 2011, NanoFab CVD CVD