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The electrical properties of BC2N thin films have been investigated in terms of the temperature dependence of the resistivity and Hall effect measurements. The BC2N thin films were prepared by chemical vapor deposition from acetonitrile and boron trichloride on polycrystalline Ni and quartz substrates. The experimental results indicated that the BC2N films were p-type semiconductors on both substrates, with acceptor levels between 7.5 and 23 meV relative to the valence band. The hole mobility on Ni substrates was one order of magnitude higher than that on the quartz substrates, suggesting that the thin film quality is better on Ni substrates than on quartz substrates.

It is pointed out that a widely used simple formula may give rise to serious errors in profiling deep level concentrations from capacitance transient experiments. A correction formula is derived based on the space-charge analysis.

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We have employed high resolution electron energy loss spectroscopy (HREELS) (in ultrahigh vacuum) to investigate the band gap of the novel semiconductor BC 2 N by measuring electronic excitations from the valence band to the conduction band. Angle-resolved HREELS allows the observation of transitions which are not vertical in k space, and the measurements indicate an indirect band structure, even though this material emits visible photoluminescence. The results also reconcile scanning tunneling microscopy and photoluminescence measurements for the system. PACS numbers: 73.61.Le, 79.20.Kz The new BC x N compounds [1][2][3][4][5][6][7] are expected to behave as semiconductors with a "tunable" band gap energy which can be controlled by their atomic composition. They are layered materials based on an atomic scale mixture of graphite, which is a semimetal [8], and boron nitride (BN), an insulator with a band gap of 6 eV. Recent research includes both experimental [1][2][3][4][5][6][7]9,10] and theoretical [11][12][13][14][15][16][17][18] studies and also extends from the layered BC x N compounds to semiconducting nanotube structures [1][2][3][4][11][12][13].Thin films of BC 2 N, which is a particularly reliable composition of the BC x N compounds, are found to be p-type semiconductors [5,6]. They represent an atomic level hybrid of the B, C, and N atoms, rather than a mixture of C and BN phases [7,19]. BC 2 N also has optical properties which are of special interest. Photoluminescence (PL) from BC 2 N, with peak intensity at wavelengths of 580-600 nm, has been reported recently [5]. The PL was observed at both 4.2 K and at room temperature, with external quantum efficiencies of .1% and .0.5%, respectively. This suggests the possibility of BC 2 N based light-emitting devices, and would normally indicate that the material has a direct band gap. However, the inferred band gap from the PL measurement of 2.1 eV [5] is not in total agreement with spectroscopic scanning tunneling microscopy (STM) results [5], which indicate a lower band gap (perhaps around 1.4 eV). Thus the nature of the band structure of BC 2 N (in particular, whether the material has a direct or indirect gap) is one which needs to be resolved.In this Letter the band structure of BC 2 N is addressed using high resolution electron energy loss spectroscopy (HREELS) in ultrahigh vacuum (UHV). HREELS measures the electronic excitations from the valence band to the conduction band. Angle-resolved HREELS allows the observation of both vertical (optical) transitions and transitions which are not vertical in k space. Measurements of the (apparent) band gap as a function of k show a negative dispersion, which indicates an indirect band structure. This observation is compared with theoretical calculations [15] and reconciles the band gap which can be inferred from scanning tunneling microscopy results for the system with the (vertical) gap obtained from photoluminescence spectra [5].The BC 2 N thin films used in this study were prepared by the chemical vapor depos...

In the left column of p. 187 and lines 35 and 36, the sentence "The acetonitrile was regulated at 24 Pa and the boron trichloride was regulated at 90 Pa," should read "The acetonitrile was regulated at 190 Pa and the boron trichloride was regulated at 1200 Pa." 2846 0031-9007͞96͞77(13)͞2846(1)$10.00

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We have studied stable structures of hydrogenated Si clusters grown from silane gas in an ion trap developed for cluster growth. The grown clusters were extracted from the ion trap through two different pathways and were analyzed by mass spectrometers. The Si6Hx+ cations were stably grown, among them clusters with x=1, 7, and 13 were always observed, regardless of the growth conditions or the extraction pathways. The stable structures of these clusters were theoretically investigated. Clusters of x=1, 7, and 13 corresponded to the compact structure, the intermediate structure which has both compact and bulklike configurations, and the bulklike sp3 structure, respectively.