Propriedades de transporte eletrônico em filmes de diamante crescidos por deposição de vapores químicos
Resumen
In this work it was investigated some fundamental properties of undoped and Borondoped
(p-type) synthetic diamond films. It was investigated the influence of the cleaning
process on the surface s quality in order to produce better metal-diamond electrical contacts.
Two cleaning processes were used: chemical and physical (thermal treatment). The
Raman spectroscopy was used as a fundamental tool in order to quantify the changes in the
samples surfaces after both treatments. It was observed an increase of the resistivity, and
consequently a decrease of the superficial conductivity. This fact was related to non-diamond
layers remotion being confirmed by current-voltage measurements. These curves show the
Space Charge Limited Currents (SCLC) as the dominant conduction process in the samples
revealing the expected insulator character of the undoped films. It was also investigated
the presence of charge localization effects (due to the presence of deep levels) using the
admittance spectroscopy. It was found two impurity centers with activation energies around
34-74 meV and 340-360 meV. They are related to the activation of non-Boron deep levels
and Boron acceptors, respectively. The most important conclusion in this case is that the
presence of these levels suggests different conduction mechanisms acting on the samples; this
hypothesis was confirmed by temperature dependent resistivity measurements. Moreover, it
was confirmed the hopping process as the dominant conduction mechanism in a large range
of temperatures. Additionally, it was determined the spatial extension of the wave function
associated to the carriers. All these previous data on the transport mechanisms in diamond
films have motivated the development of a device which was primarily designed to be used
as a temperature sensor. Characteristics such as sensibility, resolution and time response
were well determined. The device presented a reliable behavior and good reproducibility
even under influence of external parameters like light and magnetic fields.