Diamond is a promising material for several applications, due to its extreme properties. Deposition of diamond thin films on foreign substrates via microwave plasma enhanced CVD offers a possible solution when versatility of shapes, large deposition surfaces and reproducible quality are required. The use of pulsed instead of continuous discharges was explored by several groups, as it offers the possibility to add two non conventional parameters such as pulse frequency and duty cycle. In some cases, an improvement in film morphology, quality and/or growth rate was found. In the present study pulsed microwave discharges at a pulse repetition frequency of 100 Hz and variable duty cycle have been investigated via in-situ pyrometric interferometry to monitor the deposition of polycrystalline diamond films on silicon from highly dilute (1% CH4 in H2) gas mixtures. This analysis allowed to evaluate the incubation period and the growth rate. After deposition the films morphology was analysed via SEM. The results of two series of similar experiments show an increase in the growth rate with the duty cycle, with a maximum in case of continuous plasma. SEM images show few isolated large grains surrounded by much smaller features, not clearly crystalline, with duty cycle lower than 75%. More homogeneous films, in terms of orientation and grain size, are formed in case of higher duty cycle. XRD analyses and Raman spectroscopy will give information about texture and purity of the material.
Study of polycrystalline diamond deposition by continuous and pulsed discharges
G Cicala;
2009
Abstract
Diamond is a promising material for several applications, due to its extreme properties. Deposition of diamond thin films on foreign substrates via microwave plasma enhanced CVD offers a possible solution when versatility of shapes, large deposition surfaces and reproducible quality are required. The use of pulsed instead of continuous discharges was explored by several groups, as it offers the possibility to add two non conventional parameters such as pulse frequency and duty cycle. In some cases, an improvement in film morphology, quality and/or growth rate was found. In the present study pulsed microwave discharges at a pulse repetition frequency of 100 Hz and variable duty cycle have been investigated via in-situ pyrometric interferometry to monitor the deposition of polycrystalline diamond films on silicon from highly dilute (1% CH4 in H2) gas mixtures. This analysis allowed to evaluate the incubation period and the growth rate. After deposition the films morphology was analysed via SEM. The results of two series of similar experiments show an increase in the growth rate with the duty cycle, with a maximum in case of continuous plasma. SEM images show few isolated large grains surrounded by much smaller features, not clearly crystalline, with duty cycle lower than 75%. More homogeneous films, in terms of orientation and grain size, are formed in case of higher duty cycle. XRD analyses and Raman spectroscopy will give information about texture and purity of the material.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
