B. Canut

Surface modifications of LiNbO3 single crystals induced by swift heavy ions

Single crystals of LiNbO3 (Y-cut orientation) have been irradiated at GANIL using different ions (112Sn, 155Gd and 238U) accelerated in the GeV range. All the irradiations were performed at room temperature, with fluences extending from 1010 to 1012 ions cm−2. Rutherford backscattering spectrometry in channeling geometry (RBS-C) was employed to investigate the lattice disorder resulting from the high electronic stopping power (dE/dx)e (between 18 and 40 keV nm−1). Surface swelling of the irradiated samples was evidenced using a profilometer, in conjunction with direct observations in the nanometer scale by means of atomic force microscopy (AFM). According to RBS-C analysis, the damage cross section Ad varies from 4 × 10−13 to 1.4 × 10−12cm2 and depends on both (dE/dx)e and the velocity of the incident ions. A correlation was pointed out between the height of the out of plane step and the (dE/dx)e-induced damage. AFM observations, performed on samples irradiated at the lowest fluences, indicate a significant broadening of the latent track radius at the surface.

Damage induced in LiNbO3 single crystals by GeV gadolinium ions

Abstract Single crystals of LiNbO3 with two different orientations (Y-cut and Z-cut) have been irradiated at GANIL with 5.17 MeV/amu 155Gd ions at room temperature. The fluence extended from 1.5 × 1011 to 1.2 × 1012 ions cm−2. The damage resulting from the high electronic stopping power (up to 30 keV/nm) has been characterized by both Rutherford backscattering ion channeling (RBS-C) and optical absorption measurements. By using a degrader, the defect efficiency has also been investigated as a function of the electronic stopping power (18 keV/nm

Latent track formation in germanium irradiated with 20, 30 and 40 MeV fullerenes in the electronic regime

Abstract Conventional transmission electron microscopy (TEM) and high resolution electron microscopy (HREM) have been performed on irradiated germanium with a few tens of MeV C 60 incident clusters (fullerenes). Normal and inclined incidences of the beam have been investigated. As observed in the case of silicon, microscopy observations after irradiation with 20, 30 and 40 MeV beams show clearly the presence of cylindrical amorphous latent tracks of 6, 10.6 and 12.5 nm in diameter, respectively. Other microstructural considerations are reported. The difference in diameter has been interpreted in terms of high electronic energy deposited by the three different energetic fullerene beams. Furthermore, during HREM observation, a recrystallisation process of the amorphous region of the tracks has been observed and analysed.

Superoleophobic Behavior Induced by Nanofeatures on Oleophilic Surfaces

The control of surface wetting properties to produce robust and strong hydrophobic and oleophobic effects on intrinsically oleophilic surfaces is at the heart of many technological applications. In this paper, we explore the conditions to observe such effects when the roughness of the substrate is of fractal nature and consists of nanofeatures obtained by the ion track etching technique. The wetting properties were investigated using eight different liquids with surface tensions gamma varying from 18 to 72 mN m(-1). While it is observed that all the tested oils readily wet the flat substrates, it is found that the contact angles are systematically exalted on the rough surfaces even for the liquids with very low surface tension. For liquids with gamma > or = 25 mN m(-1) an oleophobic behavior is clearly induced by the nanostructuration. For liquids with gamma < 25 mN m(-1), although the contact angle is enhanced on the nanorough surfaces, it conserves its oleophilic character (theta* lower than 90 degrees). Moreover, our experiments show that even in the case of hexane, liquid having the lowest surface tension, the homogeneous wetting (Wenzel state) is never reached. This high resistance to liquid impregnation is discussed within the framework of recent approaches explaining the wetting properties of superoleophobic surfaces.

High energy heavy ion irradiation effects in α-Al2O3☆

Abstract Single crystals of Al 2 O 3 have been irradiated at GANIL with 3.5 MeV/amu Pb ions, at a temperature of ≌ 8 K. The fluence range extended from 4×10 11 to 1.2×10 12 ions cm −2 . The effects of high electronic excitation induced in the samples have been characterized by Rutherford backscattering on channeling (RBS) in conjunction with optical absorption measurements. Moreover, some samples preliminary implanted with 10 16 57 Fe + ions cm −2 at 110 keV and annealed at 1673 K during one hour were studied using conversion electron Mossbauer specroscopy (CEMS) in order to obtain complementary informations. Preliminary RBS results (77 K irradiations) indicate a damage cross section of ∼ 10 −13 cm 2 , consistent with a track radius of about 1.8 nm. The defect efficiency has been also investigated as a function of the electronic stropping power (d E /D x ) c .

Magneto-optical properties of yttrium iron garnet (YIG) thin films elaborated by radio frequency sputtering

Thin films of Yttrium Iron Garnet (YIG) are grown by radio frequency magnetron non reactive sputtering system. Thin films are crystallised by heat-treatment to obtain magneto-optical properties. On quartz substrate, the network of cracks observed on the annealed samples can be explained by the difference between the thermal expansion coefficient of substrate and YIG. The Faraday rotation of thin films is measured with a classical ellipsometric system based in transmission which allows us to obtained an accuracy of 0.01°. We studied the variation of Faraday rotation versus the applied magnetic field. The variation of the Faraday rotation is the same that this obtained by VSM (vibrating sample magnetometer) analysis. With a quartz substrate, maximum Faraday rotation is observed to be 1900°/cm at the wavelength of 594 nm for an annealing of 740°C. The variation of the Faraday rotation versus the wavelength is studied. The obtained values are comparable to those of the literature for the bulk material. In order to eliminate the stress due to the heat-treatment, we made some films on Gadolinium Gallium Garnet (GGG) which thermal expansion coefficient is near than the YIG one. The material crystallises with no cracks and the Faraday effect is equivalent.

Tin-doped indium oxide thin films deposited by sol-gel dip-coating technique

Abstract Indium tin oxide (ITO) thin films were prepared by the sol–gel dip-coating (SGDC) technique. The microstructure and electrical properties of ITO thin films crystallized using rapid thermal annealing (RTA) were compared with those of films prepared by classic thermal annealing (CTA). ITO thin films were successfully prepared by CTA at 500 °C for 30–60 min. At the same temperature of 500 °C and with a 6 min RTA treatment, the film exhibits electrical resistivity values close to the CTA ones. The crystalline structure of the ITO films was visualized by high-resolution transmission electron microscopy (HRTEM) and electron diffraction patterns compared with that of pure In 2 O 3 . The average grain size, measured from TEM micrographs, ranges from 5 to 20 nm. The process of film densification was also followed by Rutherford backscattering spectrometry (RBS).

Latent track formation in GaAs irradiated with 20, 30, and 40 MeV fullerenes

Microstructural observations of gallium arsenide single crystals irradiated with a few tens of MeV C60 incident clusters (fullerenes) were performed. Normal and grazing incidences were investigated. Similar to in the case of silicon and germanium, cylindrical amorphous tracks whose diameters vary as a function of the projectile energy were found. However, for a given energy of the clusters, the track diameters are slightly different from one material to another. Also depending on the fullerene, energy is the length of the amorphous cylinder that formed along the projectile’s path. The recrystallization process under an electron beam during transmission electron microscopy observation was analyzed and a higher growth rate for gallium arsenide compared to that of germanium was seen.

Densification of In2O3:Sn multilayered films elaborated by the dip-coating sol–gel route

Abstract Indium Tin Oxide (ITO) thin films have been deposited by the Sol–Gel Dip-Coating technique, the starting solutions being prepared from chlorides. These multilayered films were crystallized by means of a classical heat treatment at temperatures ranging from 500 to 600 °C. Five stacked layers are necessary to obtain a global electrical resistivity value of 2.9×10 −3 Ω cm, for 500 °C annealed film. The paper focuses on the study of the structure of such multilayered deposits, and on the densification process, using transmission electron microscopy, Rutherford Back-scattering Spectrometry and electrical resistivity measurements. This analysis reveals structural inhomogeneities and different crystallite growth processes as a function of annealing temperature and number of deposited layers.

Densification and crystallization of SnO2:Sb sol–gel films using excimer laser annealing

Abstract We have successfully applied laser annealing to sol–gel deposited SnO2:Sb thin films in order to achieve their crystallization. The as-deposited films are quasi-amorphous and electrically non-conductive. After laser annealing they crystallize and become conductive. This paper presents a comparative study of the laser annealed films and shows the influence of the irradiation parameters on the crystallization process and the electrical behavior of the films. Our results are quite promising in view of applying this kind of treatment to films deposited on thermally sensitive substrates (e.g. polymers).