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RISS 인기검색어
- 검색키워드
- 저자 : Janicek, Petr (검색결과 1 건)
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Ansari, Mohd Zahid,Nandi, Dip K.,Janicek, Petr,Ansari, Sajid Ali,Ramesh, Rahul,Cheon, Taehoon,Shong, Bonggeun,Kim, Soo-Hyun American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.46
<P>We present an atomic layer deposition (ALD) process for the synthesis of tin nitride (SnN<SUB><I>x</I></SUB>) thin films using tetrakis(dimethylamino) tin (TDMASn, Sn(NMe<SUB>2</SUB>)<SUB>4</SUB>) and ammonia (NH<SUB>3</SUB>) as the precursors at low deposition temperatures (70-200 °C). This newly developed ALD scheme exhibits ideal ALD features such as self-limited film growth at 150 °C. The growth per cycle (GPC) was found to be ∼0.21 nm/cycle at 70 °C, which decreased with increasing deposition temperature. Interestingly, when the deposition temperature was between 125 and 180 °C, the GPC remained almost constant at ∼0.10 nm/cycle, which suggests an ALD temperature window, whereas upon further increasing the temperature to 200 °C, the GPC considerably decreased to ∼0.04 nm/cycle. Thermodynamic analysis via density functional theory calculations showed that the self-saturation of TDMASn would occur on an NH<SUB>2</SUB>-terminated surface. Moreover, it also suggests that the condensation of a molecular precursor and the desorption of surface *NH<SUB>2</SUB> moieties would occur at lower and higher temperatures outside the ALD window, respectively. Thanks to the characteristics of ALD, this process could be used to conformally and uniformly deposit SnN<SUB><I>x</I></SUB> onto an ultranarrow dual-trench Si structure (minimum width: 15 nm; aspect ratio: ∼6.3) with ∼100% step coverage. Several analysis tools such as transmission electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy, Rutherford backscattering spectrometry, and secondary-ion mass spectrometry were used to characterize the film properties under different deposition conditions. XRD showed that a hexagonal SnN phase was obtained at a relatively low deposition temperature (100-150 °C), whereas cubic Sn<SUB>3</SUB>N<SUB>4</SUB> was formed at a higher deposition temperature (175-200 °C). The stoichiometry of these thermally grown ALD-SnN<SUB><I>x</I></SUB> films (Sn-to-N ratio) deposited at 150 °C was determined to be ∼1:0.93 with negligible impurities. The optoelectronic properties of the SnN<SUB><I>x</I></SUB> films, such as the band gap, wavelength-dependent refractive index, extinction coefficient, carrier concentration, and mobility, were further evaluated via spectroscopic ellipsometry analysis. Finally, ALD-SnN<SUB><I>x</I></SUB>-coated Ni-foam (NF) and hollow carbon nanofibers were successfully used as free-standing electrodes in electrochemical supercapacitors and in Li-ion batteries, which showed a higher charge-storage time (about eight times greater than that of the uncoated NF) and a specific capacity of ∼520 mAh/g after 100 cycles at 0.1 A/g, respectively. This enhanced performance might be due to the uniform coverage of these substrates by ALD-SnN<SUB><I>x</I></SUB>, which ensures good electric contact and mechanical stability during electrochemical reactions.</P> [FIG OMISSION]</BR>
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