Wüest M. 51 Wykes M. 82 Yamaguchi M. 17 Ybarra G. 129 Yubero F ...

JUNE 28 WEDNESDAY AFTERNOON
RIVA-TF-WeA-P.5 VAPOUR SOURCE WITH SUBMONOLAYER CONTROL. H. P.
Marques, A. R. Canário, O. M. N. D. Teodoro and A. M. C. Moutinho. CEFITEC, Departamento de
Física, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 CAPARICA,
Portugal
To achieve highly accurate controlled depositions a specially designed vapour source was developed.
It provides direct rate and thickness monitoring with submonolayer control.
This compact dosing system basically consists of an evaporation source, a quartz crystal microbalance
and a shutter. The source was intended to evaporate metals with low to medium melting temperature.
It was tested with a high purity Ag wire (99.99%) wrapped around a tungsten filament. Resistive
heating was provided by an adjustable constant current through the filament.
The microbalance and the surface are mounted on the same line with the filament in between. The
careful geometric configuration and distances of the microbalance, filament and surface are such that
only 1/10th of the amount of metal deposited on the quartz crystal is deposited on the sample surface.
Therefore the resolution of the microbalance is extended by one order of magnitude.
The direct thickness measurement by the quartz microbalance with factory parameters was checked
in a calibration experiment. For the calibration an Ag film was deposited on polycrystalline Au surface
and the growth followed with LEIS. The break at the monolayer formation was used to calibrate
the thickness measurements.
This source is being successfully used to study the growth of Ag clusters on TiO 2 . The deposition
rate is a known parameter to control the size of the nanoclusters. During the depositions the mechanical
shutter provides an accurate vapour blanking to the surface. The typical dosing rate may be
as low as 0.035 ML/min, where 1 ML corresponds to 1.4x10 15 atoms.cm -2 .
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