Elsevier

Applied Surface Science

Volume 304, 15 June 2014, Pages 29-34
Applied Surface Science

Growth of thin zirconium and zirconium oxides films on the n-GaN(0 0 0 1) surface studied by XPS and LEED

https://doi.org/10.1016/j.apsusc.2014.01.102Get rights and content

Highlights

  • The manuscript reported the formation of thin zirconium and zirconium oxides layers on the n-GaN(0 0 0 1) surface under the various conditions.

  • The evolution of the film growth has been investigated by XPS and LEED.

  • During depositions, zirconium forms different compounds. Such a varied behaviour is explained by diffusion of oxygen and nitrogen in the created interface region.

Abstract

This work presents the result of the growth of thin zirconium films on the GaN(0 0 0 1) surface under various conditions. In experiment were used the X-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED) techniques, which allowed to investigate the chemical composition, bonding environment and surface reconstruction. It is shown that zirconium forms ZrN, ZrNxOy, ZrOx and ZrO2 compounds, depending on the selected experimental conditions: the pressure and annealing temperature. Such a varied zirconium growth behaviour is explained by the diffusion of oxygen and nitrogen in the created interface region.

Introduction

The insulating oxide layers, especially used in electronic devices and sensors, were based in the past mainly on SiO2. Due to increasing miniaturization transistor gates with silicon dioxide reached the limit of the thickness for which the tunnelling current leakage has unacceptably high values [1]. Such behaviour forced attempts to find new insulating materials. The promising ones are zirconium and zirconium dioxide [2], [3]. They exhibit a high thermal stability, low thermal conductivity, high durability, very low thermal neutron absorption and high resistance to corrosion. Moreover, zirconium dioxide is a high-κ gate dielectric. All these properties cause that both Zr and ZrO2 are materials very widely used in many applications, such as catalysis, medical, biomechanical and electronic devices, fuel cell technology and photonics [4], [5], [6], [7].

On the other hand, nowadays there is a huge interest in gallium nitride. It is characterized by high thermal stability, large breakdown electric field, good electron mobility and thermal conductivity. As a wide band-gap semiconductor, gallium nitride has attracted interest due to its wide applications in light emitters and detectors, high frequency field effect transistors or high power microwaves devices [8], [9]. One of the important requirements for these systems is a more reliable and thermally stable Schottky contact on n-type GaN. A good example is ZrN/Zr/GaN structure, where the Zr/GaN interface has proper thermal stability [10], [11]. That kind of nitride-based semiconductor devices typically consist of many layers of various materials, so it is important to understand processes involved in the interfaces formation, their chemical composition and structure as well as surface reconstructions in adsorbed layers.

Section snippets

Material and methods

The samples used were 10 μm thick n-GaN (Si-doped, 1018 cm−3) deposited on Al2O3 substrates (producer: Technologies and Devices International, An Oxford Instruments Company). Typical size of samples was about 4 × 8 mm2. Before inserting into the vacuum chamber, the substrates were degreased in alcohol, washed in distilled water and dried in air. Before the Zr deposition the GaN surface was annealed in cycles at the temperature about 800 °C to remove the surface oxide and carbon contaminations.

Thin

Results and discussion

The LEED optics and the XPS analyzer were used to investigate the bonding environment and to determine the main structural characteristics of the topmost layer of the surface. Fig. 1 presents the Ga 3d, N 1s, O 1s and Zr 3p XPS spectra observed for the clean and adsorbate-covered samples in the first experiment (in UHV).

For the virgin sample, although the substrate was cleaned and annealed, there is still a small amount of oxygen detected in the XPS spectrum. That is why O 1s spectrum is also

Conclusions

The experiments performed under various condition have shown that during Zr deposition onto the n-GaN(0 0 0 1) surface zirconium oxides and nitrides are produced in a different ratio. In the experiment performed in UHV, ZrN and ZrNxOy were the dominant compounds in adlayer, while in the experiment under oxygen pressure (10−7 Torr) – ZrOx (x < 2) and ZrO2. In both cases gallium was not involved in forming the adlayer. The LEED observations and the analysis of the substrate XPS signal decrease

Acknowledgments

The work was supported by Wroclaw Research Centre EIT+ within the project “The Application of Nanotechnology in Advanced Materials” – NanoMat (POIG.01.01.02-02-002/08) co-financed by the European Regional Development Fund (operational Programme Innovative Economy, 1.1.2) and by the University of Wrocław under the grant 1347/M/IFD/13.

References (27)

  • O.H. Gwangtaek et al.

    Efects of argon+ ion bombardment on a platinum/zirconium dioxide/iridium resistive switching memory cell

    Funct. Mater. Lett.

    (2011)
  • M. Copel et al.

    Structure and stability of ultrathin zirconium oxide layers on Si(001)

    Appl. Phys. Lett.

    (2000)
  • V. Papaefthimiou et al.

    Solid oxide fuel cells: on the active surface state of nickel-ceria solid oxide fuel cell anodes during methane electrooxidation

    Adv. Energy. Mater.

    (2013)
  • Cited by (11)

    • Effects of Y addition on the microstructures and mechanical behavior of ZrO<inf>x</inf>N<inf>y</inf>/V<inf>2</inf>O<inf>3</inf>-Y nano-multilayered films

      2023, Materials Science and Engineering: A
      Citation Excerpt :

      For the N 1s spectrum, the two components in Fig. 5(c) can be fitted. The peak at 398.9 eV corresponds to the ZrN bond [35,36]. The peak at the lower energy side near 396.3 eV belongs to the Zr(N, O)-like structure [35,37].

    • Micro-mechanical investigation of (Al<inf>50</inf>Ti<inf>50</inf>)N coatings enhanced by ZrN layers in the nanolaminate architecture

      2020, Applied Surface Science
      Citation Excerpt :

      The N 1s spectrum can be fitted with three components (see Fig. 6d). Peak at 398.9 eV [42] corresponds to ZrN bonds, when more intense peak at 397.7 eV [43] can be related to TiN. The peak at the low energy side at around 396.3 eV is assigned to Ti(O,N) or Zr(N,O)-like structures [44].

    • Catalytic hydrogenation of soybean oil-derived fatty acid methyl esters over Pd supported on Zr-SBA-15 with various Zr loading levels for enhanced oxidative stability

      2018, Fuel Processing Technology
      Citation Excerpt :

      According to the literature [26], it could be epitomized that most of the Zr4+ ions were located in the silica framework rather than on the catalyst surfaces, albeit the amounts of ZrO2 clusters, which were placed nearby the superficial areas of xZr-SBA-15 materials, increased with increasing Zr/Si molar ratios. The other small doublets at a BE of about 329.0–329.6 eV and 344.3–345.4 eV were assigned to sub-oxide of Zr species, resulting from the reduction stage in the catalyst preparation (Section 2.3) [48]. The ATR-FTIR spectra of the commercial SO and the synthesized SO-FAMEs (from Section 2.5) in the range of 3500–650 cm−1 are depicted in Fig. 6a and b.

    • The fundamental surface science of wurtzite gallium nitride

      2017, Surface Science Reports
      Citation Excerpt :

      The interest was in the formation of ZrO2 high-k gate dielectric layers and ZrN/Zr/GaN Schottky contacts to n-type GaN. The samples were cleaned in alcohol and H2O prior to insertion into the UHV chamber followed by annealing in situ at 800 °C [806] or 700 °C [807], and O contamination was detectable on the nominally-clean surface. In the first of the two studies [806], Zr layers were deposited in situ followed by annealing at 700 °C.

    View all citing articles on Scopus
    View full text