Behavior of Electrodeposited Cd and Pb Schottky Junctions on CH₃-Terminated n-Si(111) Surfaces

n-Si/Cd and n-Si/Pb Schottky junctions have been prepared by electrodeposition of Cd or Pb from acidic aqueous solutions onto H-terminated and CH₃-terminated n-type Si(111) surfaces. For both nondegenerately (n-) and degenerately (n⁺-) doped H–Si(111) electrodes, Cd and Pb were readily electroplated and oxidatively stripped, consistent with a small barrier height (_b) at the Si/solution and the Si/metal junctions. Electrodeposition of Cd or Pb onto degenerately doped CH₃-terminated n⁺-Si(111) electrodes occurred at the same potentials as Cd or Pd electrodeposition onto H-terminated n⁺-Si(111). However, electrodeposition on nondegenerately doped CH₃-terminated n-Si(111) surfaces was significantly shifted to more negative applied potentials (by −130 and −347  mV, respectively), and the anodic stripping of the electrodeposited metals was severely attenuated, indicating large values of _b for contacts on nondegenerately doped n-type CH₃–Si(111) surfaces. With either Cd or Pb, current–voltage measurements on the dry, electrodeposited Schottky junctions indicated that much larger values of _b were obtained on CH₃-terminated n-Si(111) surfaces than on H-terminated n-Si(111) surfaces. Chronoamperometric data indicated that CH₃–Si(111) surfaces possessed an order-of-magnitude lower density of nucleation sites for metal electrodeposition than did H–Si(111) surfaces, attesting to the high degree of structural passivation afforded by the CH₃–Si surface modification. ©2008 The Electrochemical Society

Contents

• BODY OF ARTICLE
• Experimental
  • Materials
  • Si surface functionalization
  • Electrochemical metal deposition and solid-state device measurements
  • Characterization
• Results
  • Voltammetric responses of n-type Si(111) in aqueous Cd²⁺ and Pb²⁺ solutions
  • Chronoamperometric deposition of Cd onto H-terminated and CH₃-terminated n⁺-Si(111)
  • Electrical properties of electrochemically deposited n-Si(111)/Cd and n-Si(111)/Pb Schottky junctions
  • X-ray photoelectron spectra of Si(111) surfaces after electrodeposition of Cd and Pb
• Discussion
  • Influence of surficial CH₃-groups on the barrier height of Si/Cd and Si/Pb Schottky junctions
  • Chemical passivation of Si by CH₃ surface groups
• Conclusions
• Acknowledgments
• REFERENCES
• FIGURES
• TABLES
• FOOTNOTES