The effect of ion energy on the surface morphology of platinum film under high-frequency ion plasma sputtering

The effect of ion energy (E _i = 45–220 eV) on the sputter deposition rate and surface morphology of polycrystalline platinum films processed in high-density argon plasma of low-pressure (P = 0.08 Pa) RF induction discharge has been studied. The sputtering yield of Pt has been determined as a function of the ion energy. Analysis of the data of scanning tunneling microscopy showed a large difference between the surface profiles of samples treated at minimum and maximum ion energies in the range studied. The mechanism of Pt surface morphology modification by ion plasma sputtering is discussed.     

Material properties and growth control of undoped and Sn-doped In2O3 thin films prepared by using ion beam technologies

Undoped (IO) and Sn-doped In₂O₃ (ITO) films have been deposited on glass and polymer substrates by an advanced ion beam technologies including ion-assisted deposition (IAD), hybrid ion beam, ion beam sputter deposition (IBSD), and ion-assisted reaction (IAR). Physical and chemical properties of the oxide films and adhesion between films and substrates were improved significantly by these technologies. By using the IAD method, non-stoichiometry and microstructure of the films were controlled by changing assisted oxygen ion energy and arrival ratio of assisted oxygen ion to evaporated atoms. Relationships between structural and electrical properties in ITO films on glass substrates were intensively investigated by using the IBSD method with changing ion energy, reactive gas environment, and substrate temperature. Smooth-surface ITO films (R_rms ≤ 1 nm and R_p-v ≤ 10 nm) for organic light-emitting diodes were developed with a combination of deposition conditions with controlling microstructure of a seed layer on glass. IAR surface treatment enormously enhanced the adhesion of oxide films to polymer substrate. The different dependence of IO and ITO films' properties on the experimental parameters, such as ion energy and oxygen gas environment, will be intensively discussed.     

Parameter spaces for the nucleation and the subsequent growth of cubic boron nitride films

The data existing in the literature about the deposition of cubic boron nitride thin films were reviewed critically in order to establish the parameter spaces of c-BN nucleation and growth. The ion energy E_i, the flux ratio F (=incoming ions/incoming boron atoms), the ion mass m_i, (or the ratio Ar/N₂, respectively), and the substrate temperature T_s, had already been identified as the decisive parameters which are, however, interdependent. Earlier data collections on c-BN deposition had shown that, irrespective of the deposition technique used, a well-defined c-BN region exists in the F/E_i parameter space, in which the deposition of c-BN is possible. Similar regions exist in the F/m_i and F/T_s parameter spaces. The present collection extends these older diagrams considerably, especially to the low energy region. From this extention it can be concluded that the momentum transfer concepts proposed in the literature fail to explain the data. Furthermore, the older collections were considered valid for nucleation and growth likewise. However, in recent years data have been published showing that the boundaries of the c-BN regions are different for nucleation and growth. After successful nucleation, subsequent growth can occur either at reduced ion bombardment (either energy or flux ratio or ion mass) and also at reduced temperatures. The existing data for this parameter reduction have been collected in this paper. It will be shown that the growth depends in a similar way as the nucleation on the (interdependent) ion bombardment parameters but no longer on temperature. This means that the nucleation and growth of c-BN are based on different, although in both cases ion-induced, mechanisms.     

Effects of deposition and post-annealing conditions on electrical properties and thermal stability of TiAlN films by ion beam sputter deposition

TiAlN films were deposited by ion beam sputter deposition (IBSD) using a Ti-Al (90/10) alloy target in a nitrogen atmosphere on thermal oxidized Si wafers. Effects of ion beam voltage, substrate temperature (T_s) and post-annealing conditions on electrical properties and oxidation resistance of TiAlN films were studied. According to the experimental results, the proper kinetic energy provided good crystallinity and a dense structure of the films. Because of their better crystallinity and predomination of (200) planes, TiAlN films deposited with 900 V at low T_s (50 °C) have shown lower resistivity than those at high T_s (250 °C). They also showed better oxidation resistance. If the beam voltage was too high, it caused some damage to the film surfaces, which caused poor oxidation resistance of films. When sufficient kinetic energy was provided by the beam voltage, the mobility of adatoms was too high due to their extra thermal energy, thus reducing the crystallinity and structure density of the films. A beam voltage of 900 V and a substrate temperature of 50 °C were the optimum deposition conditions used in this research. They provided good oxidation resistance and low electrical resistivity for IBSD TiAlN films.     

An orientation competition in yttria-stabilized zirconia thin films fabricated by ion beam assisted sputtering deposition

A previously found orientation competition in ion beam sputtered yttria-stabilized zirconia thin films was studied in detail. The effects of sputtering energy and deposition angle were analyzed in ion sputtered films without assisting ions bombardment. It is found that for normally deposited films, (001) and (011) orientations are favored at low and high sputtering energy respectively. For inclined substrate deposited films, as deposition angle increases, (001), (011) and (111) orientations are advantaged in turn. The results can be attributed to the in-plane energy exchange of deposition atom and adatoms. In ion beam assisting deposited YSZ films of low assisting ions energy and current, a (001) oriented biaxial texture is gradually induced as ion energy increased. In the case of ion beam assisted inclined deposition of 45°, (001) orientation is enhanced and two preferential in-plane orientations are found coexist.     

The influence of low-energy ion bombardment on the microstructure development and mechanical properties of TiBx coatings

The influence of the deposition parameters on the growth, structure and mechanical properties of the TiB_x coatings is studied. The TiB_x coatings represent a nanocomposite system, in which random or oriented TiB₂ nanocrystallites are embedded in an amorphous matrix as is revealed by cross-sectional transmission electron microscopy. We show that low-energy ion bombardment (E_i ) of growing TiB_x coating, influences the preferred orientation of TiB₂ crystallites. The increase of ion current density (i_s) by means of negative substrate bias voltage (U_s) leads to change from random to the (0001) preferred crystal orientation whereby the electrical biasing promotes crystal growth in the coating and the (0001) texture appears gradually during the film growth. Together with the (0001) preferred orientation selection the composition B/Ti ratio was changed from 2.9 (floating potential, E_i = 8 eV) to 2.4 (E_i = 94 eV). The highest amount of oriented (0001) crystallites and highest hardness H = 53 GPa exhibit TiB_x coatings deposited at E_i = 94 eV and i_s = 2.69 mA.cm⁻².     

Growth and properties of the ion beam deposited SiOx containing DLC films

In the present study SiO_x containing diamond-like carbon (DLC) films were synthesized by the closed drift ion source from hexamethyldisiloxane vapor. Kinetics of the growth of DLC films was investigated using optical emission spectroscopy (OES). Structure, chemical composition, electrical and optical properties of the synthesized films were studied. The effects of ion beam energy were investigated. The main atomic hydrogen Balmer series lines and the intense broad CH group related peak were detected in the OES spectra registered in-situ during SiO_x containing diamond-like carbon film synthesis. The intensity ratio of H-β/CH peaks increased with the increase of applied ion beam energy. It was explained by activation of the dissociation of the hexamethyldisiloxane molecules. Changes of the structure of the diamond-like carbon films were observed for the films deposited under intense dissociation conditions.     

The energy spectra of the secondary ion emission for transition metals of the fourth period

The energy spectra of the secondary ion emission (SIE) for transition metals of the fourth period are calculated under the assumption that SIE is caused by the joint action of electron-exchange and kinetic ion emission (KIE) mechanisms. Some improvement of the KIE theory is carried out for the cases of high (of the order of tens of keV) and low (less than 2 keV) energies E_O of bombarding ions. It is found that the KIE plays an essential role in SIE, starting from the E_O value of the order of tens of keV. It is shown that the KIE energy spectra (1) are broader than the sputtering energy spectra by an order of magnitude, (2) differ essentially in both cases indicated, (3) show a peak (at high E_O in accordance with an experiment) or a break (at low E_O) near to the secondary ion energy corresponding to the KIE threshold.     

Interface structure between reactively ion plated TiO2 films and PET substrate

ESCA (electron spectroscopy for chemical analysis) has been used for studying the interface structure between PET (polythylene terephthalate) substrate and TiO₂ films produced from a metal source by reactive rf bias ion plating. The results have been compared with those for films produced by conventional electron beam evaporation. Sequential ESCA analysis and in situ argon sputter profiling have been carried out for the TiO₂ films of varying thicknesses on PET. Bombardment by high energy particles prior to deposition removes surface contamination and activates the PET surface. TiO₂ films are formed on the modified surface, which results in chemical interaction between the film and substrate. A very thin TiC_x layer observed at the interface region shows the presence of this kind of interaction. On the basis of the results, the interface structure is discussed.     

Effect of microstructure on degradation of AlN films prepared by ion beam assisted deposition

Two kinds of aluminum nitride (AlN) films were prepared by ion beam assisted deposition (IBAD) by changing the nitrogen ion beam energy; one was deposited with a 0.2 keV ion beam, showing a columnar structure, and the other was deposited with a 1.5 keV ion beam, showing a granular structure. The effect of microstructure on degradation of AlN films was studied by immersing them in aqueous HNO₃, HCl, and NaOH solutions at room temperature. Degradation was examined mainly in terms of changes in optical transmittance and surface morphology. After immersion in HNO₃ and HCl solutions, the average transmittance of the columnar film decreased gradually from the beginning of immersion, while that of the granular film maintained the initial level of transmittance for about 60 h immersion in HNO₃ solution and about 80 h immersion in HCl solution. In NaOH solution, both films were detached readily from the substrate and no remarkable difference in the degradation behavior was observed between the two films. It is concluded that the IBAD AlN films with the granular structure show higher durability against aqueous acid solutions than the films with the columnar structure.     

Effect of substrate temperature on the electrical and optical properties of electron beam evaporated indium antimonide thin films

Thin films of non-stoichiometric indium antimonide (In_0.66Sb_0.34) have been deposited by electron beam evaporation technique on glass substrates at different substrate temperatures, (300?C473 K). The films have polycrystalline nature with zinc blende structure. The decrease in electrical resistivity with increasing temperature shows semiconducting behavior. Hall measurements indicate that the films are of n-type. Optical transmission spectra of as deposited thin films have been measured at different substrate temperatures. All the electrical parameters i.e. electron mobility (??), carrier concentration (n), resistivity (??), activation energy and band gap (E _g ) have been found to be temperature dependent. Suitable explanations are given in the paper.     

Ion beam energy effects on structure and properties of diamond like carbon films deposited by closed drift ion source

In the present study DLC films deposited from acetylene gas by a closed drift ion source were investigated. Ion beam energy effects on structure as well as optical and electrical properties of the synthesized films were studied. Non-monotonic dependence of structure of the DLC films on ion beam energy was observed. The highest sp³/sp² ratio as well as highest optical transparency was observed in the case of the films synthesized by 500 eV energy ion beam. However, the bandgap of the DLC films synthesized by 500 eV energy ion beam was the lowest between all investigated samples, while resistivity non-monotonically decreased with increase of the ion beam energy. These results were explained by changes of the sp³/sp² ratio, structure of sp² bonded clusters as well as hydrogen content in the film due to the competition between the increased (decreased) ion beam energy and decreased (increased) ion/neutral ratio.     

The ion energy distributions and ion flux composition from a high power impulse magnetron sputtering discharge

The energy distribution of sputtered and ionized metal atoms as well as ions from the sputtering gas is reported for a high power impulse magnetron sputtering (HIPIMS) discharge. High power pulses were applied to a conventional planar circular magnetron Ti target. The peak power on the target surface was 1-2 kW/cm² with a duty factor of about 0.5%. Time resolved, and time averaged ion energy distributions were recorded with an energy resolving quadrupole mass spectrometer. The ion energy distributions recorded for the HIPIMS discharge are broader with maximum detected energy of 100 eV and contain a larger fraction of highly energetic ions (about 50% with E_i > 20 eV) as compared to a conventional direct current magnetron sputtering discharge. The composition of the ion flux was also determined, and reveals a high metal fraction. During the most intense moment of the discharge, the ionic flux consisted of approximately 50% Ti¹⁺, 24% Ti²⁺, 23% Ar¹⁺, and 3% Ar²⁺ ions.     

Chemical effect of inert argon beam on nitride nanolayer formed by ion implantation into GaAs surface

The composition of a nitride nanolayer formed on a GaAs(100) surface by the implantation of ions with an energy of E _i = 2.5 keV and the chemical state of nitrogen in this layer have been studied by the method of Auger electron spectroscopy. It is established that, in addition to GaN, a GaAsN solid solution phase is formed in the ion-implanted layer. The energies of N KVV Auger electron transitions in these phases are determined as E _A (GaN) = 379.8 ± 0.2 eV and E _A (GaAsN) = 382.8 ± 0.2 eV (relative to the Fermi level), which allowed the distribution of nitrogen between these phases to be evaluated as [N(GaN)] = 70% and [N(GaAsN)] = 30%. It is established that an argon ion beam produces a chemical effect on the nitride layer, which is related to a cascade mixing of the material. Under the action of the argon ion bombardment, the distribution of nitrogen in the indicated phases changes to opposite. As a result a nitride nanolayer is formed in which the narrow-bandgap semiconductor (GaAsN) predominates rather than the wide-bandgap component (GaN).     

DC magnetron sputtering of Si to form SiO2 in low-energy ion beam

Silicon dioxide (SiO₂) films were deposited by magnetron sputtering and ion-beam oxidation (IBO) in separate zones at ambient temperature. The optical and structural characteristics of the films were analyzed by spectrophotometry, Fourier transform infrared absorption spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscope. The oxygen ratio in the ion beam and the energy of ion bombardment during deposition has strong influence on the optical and physical properties of SiO₂ films. The experimental results indicated that the IBO method could finely manipulate the structure and properties of the growing films.     

Deposition of titanium nitride films onto silicon by an ion beam assisted deposition method

Titanium nitride (TiN) films were deposited onto silicon wafers using an ion beam assisted deposition (IBAD) method with an electron cyclotron resonance (ECR) ion source for ionizing the nitrogen (N₂) gas under a condition of high nitrogen ion to titanium neutral ratio. The deposition rate of the TiN films was strongly dependent on the evaporation rate, d_Ti, of Ti metal and decreased with increasing nitrogen ion current. The deposition rate can be approximated as d=βd_Ti?_N2/{1/k+?_N2}−αI, where β, k and α are proportional constants, ?_N2 is the sum rate of neutral and ionized nitrogen impinging onto the substrate, and I is the nitrogen ion current.     

Hydrophobic properties of the ion beam deposited DLC films containing SiOx

Diamond like carbon (DLC) films received considerable interest due to outstanding mechanical and tribological properties as well as chemical inertness and hydrophobicity. That combination is particularly interesting for possible application of the DLC as anti-sticking layers in novel lithographic techniques such as nanoimprint lithography, because Si, quartz and Ni - the most often used materials for imprint stamp formation - have high surface energy and, as a result, bad anti-adhesive properties. In present study, SiO_x containing DLC thin films were synthesized from hexamethyldisiloxane vapor and hydrogen gas mixture by direct ion beam deposition. Anti-sticking properties of the grown DLC thin films were evaluated measuring surface contact angle with water. Chemical composition and structure of the deposited films were investigated by X-ray photoelectron spectroscopy and FTIR spectrometry. Morphology of the films was measured by atomic force microscopy. Effects of hexamethyldisiloxane flux on structure, anti-sticking properties and surface morphology of the SiO_x containing DLC thin films were defined.     

Optical properties of swift ion beam irradiated CdTe thin films

This paper reports the effect of swift (80 MeV) oxygen (O⁺⁶) ion irradiation on the optical properties of CdTe thin films grown by conventional thermal evaporation on glass substrates. The films are found to be slightly Te-rich in composition and irradiation results no change in the elemental composition. The optical constants such as refractive index (n), absorption coefficient (α) and the optical band gap energy show significant variation in their values with increase in ion fluence. Upon irradiation the band gap energy decreased from a value of 1.53 eV to 1.46 eV whereas the refractive index (n) increased from 2.38 to 3.12 at λ = 850 nm. The photoluminescence spectrum shows high density of native defects whose density strongly depends on the ion fluence. Both analyses indicate considerable defect production after swift ion beam irradiation.     

Structural and optical properties of indium tin oxide (ITO) thin films with different compositions prepared by electron beam evaporation

Tin-doped Indium oxide thin films in different compositions (Sn = 0,5,10,15,20 at.wt%) were prepared on glass substrates at the substrate temperature of 250 °C in an oxygen atmosphere by electron beam evaporation. The structural and morphological studies were carried out by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The grain size of the ITO films decreased when increasing the dopant concentration of Sn in the In₂O₃ lattice. Optical properties of the films were studied in the UV-Visible-NIR region (300-1000 nm). The optical energy band gap (E_g), as determined by the dependence of the absorption coefficient on the photon energy at short wavelengths was found to increase from 3.61 to 3.89 eV revealing the ascending loading profile of dopant concentration. Optical Parameters, such as absorption depth, refractive index (n), extinction coefficient (k), packing density, porosity, dispersion energy and single effective oscillator energy were also studied to show the composition dependence of tin-doped indium oxide films.     

Argon ion beam and electron beam-induced damage in Cu(In,Ga)Se2 thin films

Ar ion beam and electron beam-induced damages in Cu(In,Ga)Se₂ thin films are investigated by transmission electron microscopy and X-ray energy-dispersive spectroscopy. We find that a high-energy Ar ion beam can cause severe damage in Cu(In,Ga)Se₂ surface regions by preferentially depleting Se and In. The depletion can occur with an Ar ion beam at energy as low as 0.5 keV. High-energy electron beams also cause damage in Cu(In,Ga)Se₂ thin films by preferentially depleting In and Ga. Our results imply that special care must be taken for measurements involving surface treatments using high-energy Ar ion beams or electron beams.