USE OF IN-SITU ATOMIC-FORCE MICROSCOPY TO IMAGE COPPER ELECTRODEPOSITS ON PLATINUM

In situ atomic force microscopy (AFM) was used to observe growth morph ology during copper electrodeposition on Pt(100) and Pt(111) surfaces from 0.25M CuSO4/0.5M H2SO4 containing 0, 10, and 100 muM benzotriazol e (BTA). The Pt(100) crystal was misoriented approximately 2-degrees t o give terraces that were approximately 1 mum in length and 25 to 50 a ngstrom high. Deposit morphology was monitored primarily during growth at current densities between 1 and 15 mA/cm2 under stagnant condition s. In the absence of BTA, copper selectively deposited on the larger s tep sites rather than on the smaller steps or terrace regions. From so lutions containing 10 muM BTA, copper deposited in clumps along the st eps. From solutions containing 100 mum BTA, deposition occurred withou t regard to substrate features. On Pt(111), three-dimensional nucleati on of copper was monitored at the nanoscale level during cathodic depo sition from 0.2 5M CuSO4/0.5M H2SO4. At overpotentials <70 mV, no nucl ei were observed. At 120 and 170 mV overpotential, individual 3-D clus ters were observed, and additional clusters nucleated over time. At hi gher overpotentials (greater-than-or-equal-to 200 mV), uniform nucleat ion and overlap were observed. The current transients and AFM images r ecorded during the deposition experiments were compared with theory fo r 3-D, solution-diffusion-controlled, multiple nucleation with overlap . At high overpotentials, the current transients were consistent with theory, and AFM images indicated that nucleation was three-dimensional with overlap. At low overpotentials, the current transients were not consistent with theory, and AFM images confirmed that nuclei did not o verlap.