Silicon-on-diamond material by pulsed laser technique

We present a method to bond directly silicon and diamond plates to obtain a single silicon-on-diamond material, with a carbon-silicon interface of unprecedented quality. The bonding is performed at room temperature, via picosecond 355 nm pulsed laser irradiation of the silicon-diamond interface, through the transparent diamond. The obtained material exhibits excellent mechanical strength and uniformity of the bonding, as shown by mechanical tests and analysis of the cross section based on scanning electron microscopy. The bonding is ascribed to silicon carbide nanolayers at the interface which, along with amorphous silicon nanolayers, have been quantitatively detected and evaluated by means of optical spectroscopy measurements. A physical insight into the processes occurring at the diamond-silicon interface during the pulsed irradiation and cooling has been provided by a finite element numerical model. A rationale is then given for the observed SiC bond in terms of silicon and diamond melting and inter-diffusion. A crucial outcome of the model consists in predicting the effect of the different laser beam parameters on the bonding process, thereby allowing us to obtain a well tailored procedure. An excellent quality silicon-on-diamond is now available for implementing highly integrated electronic devices for diverse application areas, ranging from pixel detectors to biosensors and prostheses for the human body.