Structural and nanomechanical properties of InN films grown on Si(1 0 0) by femtosecond pulsed laser deposition

Abstract

The structural and nanomechanical properties of InN films grown on Si(1 0 0) using femtosecond pulsed laser deposition were studied for different growth conditions. Atomic nitrogen was generated by either thermal cracking or laser-induced breakdown (LIB) of ammonia. Optical emission spectroscopy was conducted on the laser plasma and used to observe atomic nitrogen formation. An indium buffer layer was initially grown on the Si substrate at low temperature. The surface structure and morphology were investigated by in situ reflection high-energy electron diffraction, ex situ atomic force microscopy and x-ray diffraction (XRD). The results show that the initial buffer indium layers were terminated with the In(2 × 1) structure and had a smooth surface. With increased coverage, the growth mode developed from two-dimensional layers to three-dimensional islands. At room temperature (RT), formation of submicrometre islands resulted in mixed crystal structure of In and InN. As the substrate temperature was increased to 250–350 °C, the crystal structure was found to be dominated by fewer In and more InN, with only InN formed at 350 °C. The XRD patterns show that the grown InN films have wurtzite crystal structure. The film hardness near the surface was observed to increase from less than 1 GPa, characteristic of In for the sample grown at RT using the thermal cracker, to a hardness of 11 GPa at 30 nm from surface, characteristic of InN for samples grown at 350 °C by LIB. The hardness at deep indents reaches the hardness of the Si substrate of ∼12 GPa.

Elastic properties of indium nitrides grown on sapphire substrates determined by nano-indentation: In comparison with other nitrides

“…Table II compares H NI and E c of InN films reported in the literature. [17][18][19][20][21][22] Results of the present research are intermediate among the scattered hardness and Young's moduli of InN films in a variety of thicknesses and growth surfaces by various growth methods. Results for H NI and E 1101 and E a using (1101) and (1120) faced InN films, respectively, are also included in the table, though such results seem to be rather preliminary since there is a scatter of H NI and E data values among the research groups.…”

“…Results for H NI and E 1101 and E a using (1101) and (1120) faced InN films, respectively, are also included in the table, though such results seem to be rather preliminary since there is a scatter of H NI and E data values among the research groups. 19,21 In general, H NI decreases in the order of the (0001), (1101), and (1120) surface in the wurtzite-structure semiconductors, whereas Young's modulus increases in the reverse order of the [0001], <1101>, and <1120> direction due to underlying dislocation motion at atomic or microscopic scale. 34 In thinner films, it may be difficult to evaluate correct elastic properties, which may easily lead to some variations of elastic properties.…”

“…In addition, nano-indentation can elucidate elastic parameters such as Young's modulus and other moduli of a sample at RT. Indeed, some groups have adopted the nano-indentation method and evaluated the elastic moduli of InN thin film materials [17][18][19][20][21][22] although there is some scatter among the findings of hardness and moduli in the reported results, originating in the difference of growth methods and thickness of the samples employed. Thin film grown epitaxially as InN or other nitrides easily suffers effects of crystalline quality as well as those of the substrates.…”

Growth temperature effect on physical and mechanical properties of nitrogen rich InN epilayers

“…Nanoindentation technique is currently an effective method for probing mechanical features of thin films at nanoscale, without any concern about the limitation of sample size and shape [26]. However, it is noticed a large dispersion of the measured mechanical properties that were reported in literature [26][27][28]. This discrepancy is likely explained by the different growth methods used for InN epitaxy, the dissimilar growth conditions, the various InN thickness layers studied and the shape and indenter tip radius used in nanoindentation tests.…”

Epitaxial growth of semipolar InN($10\bar{1}3$) on LaAlO3substrate: Epitaxial relationship analysis

“…Various methods have been used to fabricate semipolar InN films, including radio-frequency plasma-assisted molecular beam epitaxy (RF-MBE), 16) metalorganic vapor phase epitaxy, 17) pulsed laser deposition, 18) and magnetron sputtering. 19) Although metal organic chemical-vapor deposition (MOCVD), and MBE have often been used in the growth of InN thin films, few studies have reported semipolar InN( 1013) grown directly on a LaAlO 3 substrate using RF-MOMBE.…”