ZnO is a wide and direct band-gap material (3.37 eV at room temperature) making this compound very suitable for UV
photodetector applications as well as for UV and blue light emitting devices. As an electronic conductor, ZnO may be
used as transparent and conducting electrodes for flat panel displays and solar cells. ZnO doped with various atoms can
also lead to new or enhanced functional properties. For example, doping with Al, Ga, In, Si or H allows decreasing its
resistivity to below 10-4 Ω.cm, while keeping the high optical transparency. Rare-earth doped ZnO thin films have been
studied for optics and optoelectronics such as visible or infrared emitting devices, planar optical waveguide amplifiers.
Ferromagnetic semiconductors can be obtained by doping ZnO with transition metal atoms (Mn, Co, Ni...) that could be
used as spin injectors in spintronics.
These new and exciting properties of pure and doped ZnO request the use of thin films or multilayer structures. ZnO thin
film growth by pulsed-laser deposition (PLD) with or without any dopants or alloyed atoms has been intensively studied.
In this paper, we will review the aspects of ZnO thin films grown by PLD, in order to prepare dense, stoichiometric and
crystalline epitaxied ZnO layers or to form nanocrystalline films. Then, the optical and electrical properties will be
discussed with a special emphasis on the growth conditions in relation to the physical properties for applications in p-n
junctions, light emission devices, spintronics and bandgap tuning.
In recent years Pulsed-Laser Deposition (PLD) has became increasingly popular as a viable deposition process for
numerous materials. To overcome the main drawback of this method (macroscopic particles on the surface of the films),
femtosecond (fs) lasers have been thought to be an ideal tool to obtain high quality thin films. However, it appeared that
the nature of films grown by fs PLD strongly depends on the material and growth conditions. Indeed droplets are often
observed evidencing the presence of violent thermal effects during the fs PLD process. In addition, the films are
generally constituted by the random stacking of clusters in the 10-100 nm range that may be interesting for applications
especially in the field of sensors and catalysis. In this paper, the experimental conditions leading to the formation of
films composed of cluster piles without droplets will be presented. The results will be discussed as well as the possible
explanations of the formation of clusters during fs PLD at the light of the literature produced in this field.
In this study, we have prepared BN thin films deposited on a silicon substrate using the laser ablation technique. The irradiation of boron nitride target by a NdYAG laser (with two wavelengths: 532 and 266 nm) and by an excimer laser (193 and 248 nm) leads to films which are characterized by Fourier Transform Infra-Red spectroscopy, and mainly by X-ray Photoelectron spectroscopy (XPS) and laser microprobe coupled with mass spectrometry (LAMMA). In a first step, we have investigated the laser-target interactions by XPS spectroscopy and LAMMA microprobe, in this last case, we compare the spectra both in positive and negative modes obtained by analysis of the different films (realized by laser ablation deposition at 266 nm) with those of reference materials: BN (target used for the films synthesis) and B2O3 (oxide which could be formed in laser ablation experiment). The results underline the role of the oxygen traces in the synthesis vacuum chamber leading to a film in which oxygen is inserted in the boron nitride lattice but not under the B2O3 structure. On the other hand, the XPS analysis of the films realized at 532 and 266 nm show that the boron is found in two different states: the first one corresponds to the boron bound to nitrogen (BN) and the second one is attributed to the elementary boron with oxidation state zero. All the analysis performed on the films prompt us to conclude that elementary boron detected by XPS experiments is formed during laser ablation leading to nitrogen deficient films. Finally, we show that the laser ablation of the boron nitride target with the 248 nm laser wavelength allows to obtain a thin film in which the boron is detected in only one state of binding (boron bound to nitrogen) by XPS spectroscopy. The profitable effect of the 248 nm laser irradiation on the stoichiometry of the obtained BN film could be due to the Band-Gap absorption phenomena.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.