Cross-beam Pulsed Laser Deposition Research Articles

Structural investigations of laser-deposited Fe/Al multilayers

Fe/Al multilayers are prepared by crossed-beam pulsed laser deposition and investigated by Rutherford backscattering, conversion electron Mossbauer spectroscopy, and transmission electron microscopy. The results are compared to purely ballistic simulations of the deposition process using the TRIDYN4.0 code. It is found that the intermixing of adjacent layers must be described in terms of ballistic mixing followed by chemical mixing. The phase formation in the transition layer between adjacent layers follows the non-equilibrium behavior of Fe/Al in analogy to investigations on mechanically alloyed and ion-beam-mixed Fe/Al. In Fe-rich areas a bcc solid solution is formed. In Al-rich environment an amorphous phase is observed.

Crossed Beam Pulsed Laser Deposition of cryolite thin films

To deposit cryolite thin films with a composition close to the correct stoichiometry on a silicon substrate, a Direct Pulsed Laser Deposition (DPLD) set-up and a Crossed Beam Pulsed Laser Deposition (CBPLD) set-up have been used. In the case of CBPLD two targets are simultaneously ablated and the two ablation plumes are crossing at 15 mm from the targets. With the two different set-up thin films present a composition close to the correct stoichiometry (Na 3AlF 6). The surface of thin films deposited by DPLD shows a very high droplets density. At the opposite the CBPLD allows to decrease dramatically this density. Furthermore fast CCD-photographs of the plasmas have been used to study plumes expansion with the two different set-up. With the CBPLD one, the two plasmas interaction has been studied and their expansions have been compared with the one observed when only one target is ablated. The trajectories redistribution of the ablated species due to the collision of the two plasma clouds is clearly visible.

Spatio-energetical characteristics of laser plasma in cross-beam pulsed laser deposition

Effective droplet filtering without considerable loss of ablated material is demonstrated in the cross-beam pulsed laser deposition (CBPLD). Time-of-flight (TOF) measurements have been carried out with ion collectors in order to obtain kinetic energy distribution functions of ionized particles in the CBPLD plasma. The average and maximal kinetic energies of the ions in the CBPLD have proved to be of order 100 eV and 800 eV respectively, i.e., 2–3 times lower as compared to conventional PLD.

Growth of GaN(0001) thin films on Si(001) by pulsed reactive crossed-beam laser ablation using liquid Ga and N2

Wurtzitic GaN films were grown by reactive crossed-beam pulsed laser deposition at 248 nm (KrF) using a liquid Ga target and a synchronous N2 pulse on atomically flat, initially two domain 2×1 reconstructed Si(001) substrates. The films were (0001) single phase for substrate temperatures between 200 and 700 °C, and also grew in a twinned epitaxial manner with the crystallites oriented parallel to the [110] and [1̄10] in-plane directions of the Si(001) substrate between 550 and 700 °C. Above 700 °C, no GaN could be detected and only Ga liquid films were produced. The films were subsequently investigated ex situ by x-ray diffraction, reflection high-energy electron diffraction, and photoluminescence.

Nanopatterning by biological templating and laser direct writing in thin laser deposited films

We report on three alternative approaches to laser-supported sub-micro- and nanopatterning of ultrathin films. The inherent non-linearities of direct writing techniques can be used to fabricate structures far below the optical resolution limit. Due to the non-linear dependence of light absorption and reaction rate on film thickness and temperature (a) the lateral self-limitation of the oxidation reaction in ultrathin titanium films on a transparent heat insulating substrate in air can occur. The polarization of sharp conducting tips results in (b) near-field enhancement of the optical field in nanometer regions that allows diminishing of the effective size of the radiation source. The third approach (c) is based on the nanometer-period pattern transfer from a biomolecular template to a Pt/C overlayer deposited by cross-beam pulsed laser deposition.