P. Prieto

SiCN alloys deposited by electron cyclotron resonance plasma chemical vapor deposition

Silicon–carbon–nitrogen alloys have been deposited by electron cyclotron resonance plasma chemical vapor deposition. Nitrogen, methane, and argon diluted silane have been used as precursor gases. The properties of the deposited films were studied by spectroscopic ellipsometry, Fourier transform infrared spectroscopy, X‐ray photoelectron, and Auger electron spectroscopy. The structure and bond formation in the SiCN films is discussed in terms of the present results.

Thermal oxidation of TiN studied by means of soft x‐ray absorption spectroscopy

The oxidation of TiN in an oxygen flow at temperatures in the range 300–500 °C has been studied by means of soft x‐ray absorption spectroscopy. The analysis of the experimental results indicates that O progressively displaces N to form TiO2. The process appears to be controlled by the temperature dependence of the oxygen diffusion. Some oxidation is observed to take place even at room temperature. No evidence of oxynitride formation was found in thermally oxidized TiN, instead complete phase separation is observed. The interface between TiO2 and TiN seems to be very abrupt. The appearance of a sharp absorption peak in the N 1s spectrum of TiN is believed to be due to nitrogen atoms which are displaced during the oxidation process and remain unbounded within the TiO2 matrix. For temperatures above 400 °C, this peak disappears as the interstitial N atoms migrate to the surface and desorb.

Dielectric properties of Zr, ZrN, Zr3N4, and ZrO2 determined by quantitative analysis of electron energy loss spectra

The dielectric properties of Zr, ZrN, Zr3N4, and ZrO2 in the energy range from 1 to 80 eV were determined by quantitative analysis of electron energy loss spectroscopy in the reflection mode (REELS) using a recently proposed model. Collective excitations and electronic transitions are well characterized in the REELS spectra after analysis of the respective energy loss function, real and imaginary parts of the dielectric constant, and the optical joint density of states for the four compounds studied here.

The electronic structure of TiN and VN: X-ray and electron spectra compared to band structure calculations

We studied the electronic structure of TiN and VN by means of band structure calculations and spectroscopic techniques. The band structure calculations show that the bonding in these compounds is mostly covalent. The Fermi level intersects the transition metal 3d bands giving rise to the metallic conductivity observed in these nitrides. The particularly large stability of these compounds is due to filled metal 3d-nitrogen 2p bonding states. The X-ray photoemission (XPS) and the N 1s X-ray absorption (XAS) spectra are related to the occupied electronic states in the valence band and to the unoccupied electronic states in the conduction band respectively.

CHARACTERIZATION OF CARBON NITRIDE THIN FILMS PREPARED BY DUAL ION BEAM SPUTTERING

Carbon nitride thin films obtained by dual ion beam sputtering have been investigated by electron energy‐loss spectroscopy (EELS), transmission electron microscopy, and Fourier transform infrared spectroscopy. The nitrogen content in the films depends on deposition conditions. A maximum value of N/C=0.8 has been achieved. A new peak at 286.7 eV energy loss in the C K‐edge EELS spectra has been assigned to C=N bonds with C in the sp2 hybridization state. In addition, experimental evidences are presented of the formation of β‐C3N4 crystallites embedded in a layer of a polymer like CNx amorphous phase. An evaluation of the experimental parameters that lead to the highest N content in the films is also included.

Bonding and morphology study of carbon nitride films obtained by dual ion beam sputtering

Thin carbon–nitrogen films (i.e., CNx) have been obtained by dual ion beam sputtering. The chemical composition and the type of bonding of the CNx material have been examined, as a function of the deposition parameters, by Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy (XPS), and electron energy loss spectroscopy (EELS). The high concentration of C≡N bonds present in some of the samples, as stated by FT-IR, allowed us to correlate this type of bonding with some of the features observed in the corresponding XPS and EELS spectra. Nitrogen concentrations of up to 45 at. %, depending on the deposition conditions, have been estimated by XPS and EELS. The films deposited at low energy were rather homogeneous, as demonstrated by Auger electron spectroscopy depth profiling, and show the highest C–N simple bonds concentration. On the contrary, the use of high energy assisting nitrogen ions leads to the formation of carbonitrile groups (i.e., C≡N), as well as resputtering effects that significantly reduce the thickness of the films and even hinder the growth of a film. The topography and morphology of the different films, as determined by atomic force microscopy, were also observed to depend on the conditions of assistance.Thin carbon–nitrogen films (i.e., CNx) have been obtained by dual ion beam sputtering. The chemical composition and the type of bonding of the CNx material have been examined, as a function of the deposition parameters, by Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy (XPS), and electron energy loss spectroscopy (EELS). The high concentration of C≡N bonds present in some of the samples, as stated by FT-IR, allowed us to correlate this type of bonding with some of the features observed in the corresponding XPS and EELS spectra. Nitrogen concentrations of up to 45 at. %, depending on the deposition conditions, have been estimated by XPS and EELS. The films deposited at low energy were rather homogeneous, as demonstrated by Auger electron spectroscopy depth profiling, and show the highest C–N simple bonds concentration. On the contrary, the use of high energy assisting nitrogen ions leads to the formation of carbonitrile groups (i.e., C≡N), as well as resputtering effects that sig...

Electronic structure and chemical characterization of ultrathin insulating films

Abstract We report on the use of photoemission to probe the electronic structure of ultrathin films. The electronic structure of Zr 3 N 4 grown by low energy N 2 + implantation in polycrystalline zirconium has been investigated. The insulating characteristics of Zr 3 N 4 as well as the metal–insulator phase transition in ZrN x , when x approaches 1.33, can be nicely observed by photoemission during the implantation process. Other examples correspond to the understanding of oxide/oxide interfaces by in situ characterization of the growth of an oxide film on a dissimilar oxide. We have studied the electronic properties of the TiO 2 /SiO 2 interface by examining the O 2p valence band and the O 2s and Ti 3p core levels during growth of ultrathin films of TiO 2 on SiO 2 . We report evidence for the formation of cross linking oxygen ions to form Si O Ti bonds at the interface. In addition we use the high sensitivity of the Ni 2p XPS core level lineshape to the local co-ordination of the nickel atoms to study the interface NiO/MgO(100) by in situ characterization of the growth of ultrathin NiO films on MgO(100).

Carbon nitride films synthesized by dual ion beam sputtering

Abstract Carbon nitride films CNx have been obtained in a dual ion beam sputtering system using Ar+ to deposite graphite and low energy (i.e.

Growth, structural, and magnetic characterizations of nanocrystalline γ′-FeNiN(220) thin films

The authors have developed a fabrication process of nanocrystalline γ′-FeNiN[220] thin ferromagnetic films by using a dual ion beam sputtering system. The films show well defined in-plane magnetic uniaxial anisotropy, with high anisotropy field and high macroscopic saturation magnetization, requisites of crucial importance for high-frequency applications. The estimated ferromagnetic resonance frequency goes within the gigahertz regime, and the magnetic response can be tailored by the deposition conditions. Element-selective measurements reveal a reduction of the total Fe and Ni magnetic moments in γ′-FeNiN with respect to pure Fe and Ni due to hybridization between Fe and Ni 3d and N 2p states.

SiBCN synthesis by high-dose N++C++BF2+ ion implantation

High-dose implantation processes of N++C++BF2+ have been performed on Si(100) substrates at 600 °C. Additional simple (N+,C+) and double (N++C+ and N++BF2+) implantations have also been produced to sequentially study the synthesis of different semiconductor compounds. FTIR spectra of all the samples before and after thermal annealing at 1200 °C have been acquired. When N+ and C+ are co-implanted the formation of a ternary phase of SiCN nature is suggested, meanwhile in the case of N+ and BF2+ competition between BN and Si3N4 takes place. The sequential implantation of the three species produces a stable surface region as deduced from the AES profiles. IR and XPS measurements suggest the formation of a SiCBxNy mainly formed by SiC with a significant content of B and N (∼20%).High-dose implantation processes of N++C++BF2+ have been performed on Si(100) substrates at 600 °C. Additional simple (N+,C+) and double (N++C+ and N++BF2+) implantations have also been produced to sequentially study the synthesis of different semiconductor compounds. FTIR spectra of all the samples before and after thermal annealing at 1200 °C have been acquired. When N+ and C+ are co-implanted the formation of a ternary phase of SiCN nature is suggested, meanwhile in the case of N+ and BF2+ competition between BN and Si3N4 takes place. The sequential implantation of the three species produces a stable surface region as deduced from the AES profiles. IR and XPS measurements suggest the formation of a SiCBxNy mainly formed by SiC with a significant content of B and N (∼20%).