Related Experiment Videos
Alkene/diamond liquid/solid interface characterization using internal photoemission spectroscopy.
C E Nebel1, D Shin, D Takeuchi
1Diamond Research Center, AIST, Central 2, Tsukuba 305-8568, Japan.
Langmuir : the ACS Journal of Surfaces and Colloids
|June 14, 2006
Summary
Researchers studied the photochemical attachment of trifluoroacetic acid-protected amino-decene (TFAAD) molecules onto diamond surfaces. They found a specific electron excitation and tunneling mechanism facilitates this bonding, with a saturation time of 7 hours.
Area of Science:
- Surface Science and Chemistry
- Materials Science
- Nanotechnology
Background:
- Single-crystalline chemical vapor deposited (CVD) diamond offers a unique platform due to its low defect density and negative electron affinity.
- Photochemical functionalization is a key technique for modifying diamond surfaces for electronic and sensing applications.
- Understanding the precise mechanisms of molecule attachment is crucial for controlling surface properties.
Purpose of the Study:
- To characterize the photochemical attachment of trifluoroacetic acid-protected 10-amino-dec-1-ene (TFAAD) molecules onto hydrogen-terminated CVD diamond.
- To elucidate the underlying electron excitation and tunneling processes involved in the alkene-diamond heterostructure formation.
- To determine the optimal conditions and time required for achieving a saturated TFAAD molecular layer.
Main Methods:
- Utilized a suite of spectroscopic techniques including total photoyield spectroscopy (TPYS), conductivity, Hall-effect, spectrally resolved photoconductivity (SPC), and optical transmission.
- Employed in situ internal photoemission (IPE) spectroscopy in the 4–6 eV range for the first time on these heterostructures.
- Applied X-ray photoelectron spectroscopy (XPS) to analyze the chemical bonding of TFAAD molecules to the diamond surface.
Main Results:
- Spectroscopic data confirmed that the photochemical reaction window is below the diamond's optical gap due to negative electron affinity.
- In situ IPE experiments revealed electron emission between 4.5 and 5.2 eV, supporting a model of valence-band electron excitation to surface states followed by tunneling.
- Experimentally determined a saturated TFAAD layer of approximately 2 x 10^14 cm^-2 is achieved in 7 hours, with a low bonding efficiency of 1 molecule per 1600 emitted electrons.
Conclusions:
- The study established a detailed mechanism for TFAAD molecule attachment to hydrogen-terminated diamond via photo-induced electron excitation and tunneling.
- The findings provide critical insights into the surface chemistry and electronic properties of functionalized diamond.
- This work paves the way for controlled surface modification of diamond for advanced electronic and sensing applications.