Manganese dioxide (MnO2) is considered as one of the most attractive compound among the manganese oxide phases
due to its fundamental chemical and physical properties, its use in energy-storage devices, electrochemical applications,
and biosensors. There have been limited attempts to grow high quality MnO2 thin films where high pressure and low
substrate temperature are targeted to promote the formation of this phase. In this work, we have exploited the flexibility
of Pulsed Laser Deposition (PLD) in order to synthesize thin films of MnO2 on Si substrates by laser ablation of a MnO
target in oxygen gas ambient. Substrate temperature was varied from 25 to 800 °C aiming to grow films of good
crystalline quality while investigating the temperature range where MnO2 phase is expected to be stable. We have also investigated the effect of oxygen pressure which was varied from 10 to 500 mTorr. X-ray diffraction and Fourier Transform Infra-Red analyses have confirmed the formation of the MnO2 phase for pressures above 250 mTorr, and an optimal deposition temperature of 500 °C, while Mn2O3 is obtained in the range between 550 and 650 °C. Further increase in deposition temperature led to pure Mn3O4 films. Atomic Force Microscopy imaging confirms the nanograined surface structure of the MnO2 films, with a typical grain size of 30 nm.
We present a novel approach to enhance light emission in Si and demonstrate sub-bandgap light-emitting diodes (LED) based on the introduction of point defects. Ion implantation, pulsed laser melting and rapid thermal annealing were used to create LEDs containing self-interstitial-rich optically active regions. Procedures to fabricate LEDs on a bulk silicon substrate and on a silicon-on-insulator (SOI) wafer will be presented, and methods to improve device performances will be discussed. The control and utilization of point defects represents a new approach toward creating Si in a stable, optically active form for Si-based optoelectronics.
The interaction of the highly energetic pulsed excimer laser beam with a target material induces non-equilibrium physico-chemical processes which could be harnessed to synthesize a variety of novel and technologically attractive materials that are difficult to grow using more conventional thin film deposition techniques. In this paper, recent advances on two excimer laser based techniques that we have used in the processing of thin films and surfaces will be presented. First, we demonstrate the synthesis, by Pulsed Laser Melting (PLM), of silicon supersaturated with sulfur at concentrations several orders of magnitude greater than the solubility limit of silicon alloys, with strong sub-bandgap optical absorption. This material has potential applications in the fabrication of Si-based opto-electronic devices. Second, the capability of Remote Plasma Pulsed Laser Deposition (RP-PLD) in synthesizing the meta-stable half-metallic CrO2 compound that is of great interest in the field of spintronics was assessed. Infra-Red spectroscopy and Magnetic Force Microscopy indicate that the use of the remote plasma is beneficial to the formation of the CrO2 phase, at a deposition pressure of 30 mTorr and for deposition temperature below 350 °C. Atomic Force Microscopy and Magnetic Force Microscopy studies respectively show that films containing the CrO2 phase have significantly different surface topography and magnetic characteristics from those in which the Cr2O3 phase is dominant.
We have investigated both the large area excimer laser-induced deposition of W and it silicides on GaAs to form thermally stable Schottky contacts, and the reduction of Cu(I) and Cu(II) compounds for the deposition of Cu interconnects for Si microelectronics. Using a KrF excimer laser at 25 mJ/cm2 and a mixture of WF6, SiH4 and Ar, metallic W is deposited with an average growth rate of 1 angstrom/pulse. For Cu deposition, the precursor Cu(hfac)(TMVS) gives much purer deposits than the Cu(II) compounds which have been studied. For both processes, possible deposition mechanisms are discussed in terms of gas phase and surface reactions.
Conference Committee Involvement (1)
Laser Applications in Microelectronic and Optoelectronic Manufacturing XIII
21 January 2008 | San Jose, California, United States