Reactive Ionized Cluster Beam Deposition Research Articles

Characterization of CN x films by X-ray emission measurements

Carbon Kα and nitrogen Kα X-ray emission spectra (XES) excited by monochromatic synchrotron radiation have been used to characterize carbon nitride films (N/C ratio 0.25, mass density 2.6 g/cm 3) synthesized by reactive ionized cluster beam deposition. XES measurements of these carbon nitride films show a predominant proportion of sp 2 bonded carbon and nitrogen atoms.

Growth stage of crystalline Y2O3 film on Si(100) grown by an ionized cluster beam deposition

We investigated the initial and epitaxial growth stage of Y2O3/Si(100) grown by reactive ionized cluster beam deposition, using x-ray diffraction (XRD), atomic force microscope, and reflection high-energy electron diffraction. We also investigated the crystalline structure of the films using transmission electron microscopy and XRD. The preferred growth direction of Y2O3 grown by an ion beam changed completely from the 〈111〉 to the 〈110〉 orientation in order to minimize the overall energy of the film as the substrate temperature increased. In addition to the kinetic energy of the deposited atoms, oxygen partial pressure and the substrate surface state also bear a relationship to the change in the preferred growth direction. The crystalline growth of Y2O3 film depends on the state of the surface at the initial growth stage, whether the Si surface was first exposed to oxygen or yttrium. In particular, the silicon oxide layer which formed on the Si surface during the initial growth stage played an important role in the epitaxial growth as well as the preferred growth direction of Y2O3 film.

Structural and tribological characteristics of carbon nitride films deposited by the reactive ionized-cluster beam technique

Abstract A reactive ionized-cluster beam deposition system was used to synthesize carbon nitride films. Raman scattering analysis shows the existence of a characteristic peak due to covalent C–N single bonds. This is consistent with the results of Fourier transform infrared and X-ray photoelectron spectroscopic measurements. The deposited films exhibit an extremely high hardness of 6200 kgf mm −2 . The friction and wear behavior of these films without any lubrication were measured by a reciprocating-motion ball-on-disk tribometer. It is noted that the deposited films have low initial and steady-state friction coefficients in the range 0.08–0.14. The wear rates of carbon nitride films are significantly lower than that of carbon thin films prepared by the same deposition system and evaluated under similar test conditions. These results are very encouraging for the tribological applications of carbon nitride films.

Epitaxial growth of Y2O3 films on Si(100) without an interfacial oxide layer

Heteroepitaxial Y2O3 films were grown on Si(100) substrates by the technique of reactive ionized cluster beam deposition. The crystallinity of the films was investigated with reflection high energy electron diffraction (RHEED), glancing angle x-ray diffraction (GXRD), and the interface was examined by high resolution transmission electron microscopy (HRTEM). Under the condition of 5 kV acceleration voltage at the substrate temperature of 800 °C, the Y2O3 film grows epitaxially on the Si(100) substrate. RHEED and GXRD results revealed that the epitaxial relationship between Y2O3 and Si(100) is Y2O3(110)//Si(100), and HRTEM observation showed a sharp interface without an amorphous layer.

Investigations on structural properties of carbon nitride films synthesized by reactive ionized cluster beam deposition

Carbon nitride thin films have been prepared by reactive ionized cluster beam (RICB) technique, using low molecular weight polyethylene as evaporation material and NH 3, N 2 as reactive gas. Rutherford backscattering measurements show that the composition ratio, N C , as high as 0.67, can be obtained. Transmission electron microscopy investigations suggest that the films contain the crystalline β-C 3N 4 phase. Infrared absorption measurements indicate that chemical bonds are formed between carbon and nitrogen atoms. The results also show that the structure of the films varied mainly with the RICB parameters: ionization current and acceleration voltage.

Characteristics of Y2O3 films on Si(100) by ionized cluster beam deposition

ABSTRACTIn this study, the Y2O3 films on p-type Si(100) have been fabricated by UHV reactive ionized cluster beam deposition(r-ICB) systems. The crystallinity of the films was investigated by glancing X-ray diffraction(GXRD) and in-situ reflection of high energy electron diffraction(RHEED) analyses. The results show that the preferentially oriented crystallinity of the films was increased with acceleration voltages as well as substrate temperatures. Especially, at the substrate temperature of 700 °C and the acceleration voltage of 5kV, the Y2O3 films grow epitaxially in direction of Y2O3(110)//Si(100). The characteristics of Al/Y2O3/Si MIS structure were obtained by C-V, and I-V measurements. The breakdown field strength of the epitaxially grown films increases up to 2MV/cm without any interface silicon oxide layer, and the dielectric constant is found to be ε=15.6. these results demonstrated that the yttrium oxide films have potential application to the gate insulator of the future VLSI/ULSI devices.

Heteroepitaxial growth of Y 2O 3 films on Si(100) by reactive ionized cluster beam deposition

Heteroepitaxial Y 2O 3 films on Si(100) have been grown by the technique of reactive ionized cluster beam (ICB) deposition. The composition of deposited film is investigated by using the X-ray photoelectron spectroscopy (XPS). It was found that the composition ratio of Y to O is 1 to 1.46. Using reflection high energy electron diffraction (RHEED) and glancing angle X-ray diffraction (GXRD), we study the crystallinity of the films. It was noticed that the orientation of deposited film is mainly determined by the substrate temperature and the cluster acceleration energy. We also found that, without acceleration below 800°C, Y 2O 3 films were grown as polycrystalline. Under the condition of 5 kV acceleration voltage above 650°C, we noticed the heteroepitaxial growth of Y 2O 3 film on Si(100) substrate. The epitaxial relationship between Y 2O 3 and Si(100) is presented as Y 2O 3(110)//Si(100) and Y 2O 3[110]//Si[100] or Y 2O 3(110)//Si(100) and Y 2O 3[100]//Si[100].

Growth of CN films by reactive ionized cluster beam deposition

Growth of CN films on Si(111) is realized by reactive ionized cluster beam deposition (RICBD). X-ray diffraction (XRD) shows the occurrence of new CN compound which is supposed to be β-C 3N 4 in the films. Reflection high-energy electron diffraction (RHEED) demonstrated the coexistence of amorphous and crystalline CN compounds. Single bonded CN and triple bonded CN were identified by infrared absorption spectra. X-ray photoelectron spectra show 20% N incorporated into the films and certify the bonding energy of C 1s and N 1s. Two peaks are observed in C 1s and N 1s core level spectra. The Knoop hardness of CN films is related to accelerating voltage and ionizing current, and reaches 6200 kgf/mm 2.

Combined EPMA and AES depth profiling of a multilayer Ti-Al-O-N coating

In order to compare thin-film electron probe microanalysis (EPMA) and Auger electron spectroscopy (AES) regarding reliability in quantifying chemical compositions of Ti-Al-O-N coatings with depth, a multilayer was prepared on a silicon wafer by using reactive ionized cluster beam deposition technique. Within a total thickness of about 25 nm the composition of the multilayer varied step by step from Ti-Al-O-N at the bottom to Al-O at the top. AES and, as an innovation, EPMA crater edge profiling was applied to measure the composition with depth. For quantification special thin-film EPMA techniques based on Monte Carlo simulations were applied. The chemical binding states of Al and Ti with depth were analysed using a high resolution energy analyser (MAC 3) for the AES investigations working in the direct mode. According to the deposition procedure the concentration profiles of the components varied with depth for both AES and EPMA measurements. AES provided a better depth resolution than EPMA. To get a true calibration of the depth scale an in-situ measurement method like an optical interferometry will be required. Assuming that the relative sensitivity factors are available AES depth profiling delivers concentration profiles with good accuracy. The new EPMA application provided quantitative depth profiles concerning concentration and coverage. For EPMA crater edge profiling the coating needs to be deposited on a foreign substrate because depth distributions of elements being present in both the layer and the substrate cannot be resolved. The combination of AES-depth profiling with EPMA crater edge profiling techniques is a powerful tool to analyse heterostructures quantitatively.

Preparation of PbTiO3 Thin Films by Reactive Ionized Cluster Beam Deposition

PbTiO3 thin films were prepared by reactive ionized cluster beam (R-ICB) deposition on highly (100)-oriented Pt films formed on SiO2/Si substrates. PbTiO3 thin films consisting of c-axis- and a-axis-oriented crystallines with perovskite structure were obtained at a comparatively low substrate temperature of 430°C. We think tensile stress exists in PbTiO3 thin films, and it may be the cause of a-axis orientation. It is considered that fabricating high-density PbTiO3 thin films by applying an acceleration voltage decreases the tensile stress in the film and is advantageous for preparation of c-axis-oriented PbTiO3 thin films.

Low temperature homo- and hetero-epitaxy of sapphire films by reactive ionized cluster beam deposition

The epitaxial growth of sapphire films on sapphire substrates and single crystalline Al film substrates is reported. The films were grown by Al deposition in O 2 atmosphere. O 2 gas was introduced in the chamber through a variable leak valve to 2 × 10 −4 Torr. Depositions were made at the acceleration voltages of 1–5 kV and substrate temperatures of 200–600°C. The typical deposition rate was 2 nm/min. The crystalline state could be controlled by changing the acceleration voltage. High quality epitaxial films on sapphire substrates were obtained at 5 kV and 400°C. The refractive index was 1.763. In the case of the deposition on an Al film surface, the (0001) plane of the grown film was parallel to the (111) plane of the Al film. The highest index, 1.763, was obtained on the 200°C substrate. This is almost equal to that of a sapphire crystal. The microhardness was also evaluated.

Fabrication of AIN thin films by reactive ionized cluster beam deposition technique

Low temperature and low damage deposition of insulating films on III–V compound semiconductors is of great importance for high speed devices and optoelectronic devices. The Reactive Ionized Cluster Beam (R-ICB) deposition technique is expected to provide such a process. We have modified the R-ICB deposition technique by using activated neutral species from rf plasma beam gun to obtain AIN films without damage, instead of using a reactive gas environment of 10 −4 Pa. The plasma beam gun has been utilized also for the cleaning pre-treatment. We have found that the combination of the modified R-ICB deposition technique and proper pre-treatment is promising to provide a MIS structure of a good electric property for GaAs. We have also shown that in-situ ellipsometry is a powerful tool to investigate the pre-treatment and the deposition process.

Electrical properties of TiO2 films deposited by a reactive-ionized cluster beam

Titanium dioxide films of 100–450-nm thickness were deposited on fused quartz and silicon substrates heated at 350 °C by a reactive-ionized cluster-beam deposition. After the deposition, films were annealed at 600 °C in dry O2 ambient. The electrical properties of TiO2 films and the TiO2-Si interface were analyzed. The dielectric constant of the film after the annealing was in a range of 35–108, which depended on the deposition conditions. The films showed a high breakdown voltage and a sufficiently low interface-state density of 1–2×1011 cm−2 eV−1 at the midgap.

Ellipsometric study of low-temperature silicon surface cleaning during the process of reactive ionized cluster beam deposition

The results of in situ ellipsometric measurements on silicon surfaces ttreated by ionized gas bombardment are presented. The study was performed to investigate the surface phenomena that were thought to take place during the surface cleaning process at low temperature. It is shown that there are some explicit differences in the surface effects between ionized argon gas bombardment and ionized H 2 gas bombardment. We observed that both argon and H 2 have some shortcomings as cleaning gases when silicon substrates are cleaned to obtain the clean surfaces required for thin formation. We suggest an improved surface cleaning technique which consists of the sequential combination of ionized argon gas bombardment and ionized H 2 gas bombardment. This technique can provide a clean and flat surface at low substrate temperature.

Characteristics of TiO2 films deposited by a reactive ionized cluster beam

Titanium oxides films of 150–400 nm thickness were deposited on glass and Si substrates by reactive ionized cluster beam deposition. Characteristics of films deposited at different deposition conditions of oxygen partial pressure, ionization current, and acceleration voltage have been examined. The films prepared at an oxygen pressure of 1–2×10−4 Torr showed stoichiometry of TiO2. The film is a mixture of anatase and rutile structures. By increasing the ionization current from 0 to 400 mA, the refractive index of the film could be increased from 2.0 to 2.6. By deposition at a high ionization current, the film showed rutile structure, whereas the anatase structure could be formed at a low ionization current. The optical absorption of the films is low when the films are deposited at a higher acceleration voltage.

Properties of ZnO films prepared by reactive ionized cluster beam deposition

A new film formation technique, Reactive Ionized Cluster Beam (R-ICB) deposition, is studied to provide metal oxide or nitride thin film devices. Crystallographic and electrical properties of ZnO films prepared by this technique arc described to investigate the characteristics of R-ICB technique. The major results obtained are as follows: (1) the film formation process is closely related to the acceleration voltage ( V a) applied to the Zn clusters and the reactive gas, and to the ionized cluster content in the cluster beam which is determined by the electron current for ionization ( I e); (2) epitaxial growth is realized by using sapphire substrates, and thin films deposited onto glass substrates arc preferentially oriented with the c-axis normal to the substrate when V a is in the range of 0 to 500V; (3) films with surface conductivities of 10−10 −7V cm −1 are obtained by controlling the growth rate and the acceleration voltages without annealing; (4) cathodoluminescencc spectra of films deposited by R-ICB arc similar to those of a flux grown crystal.