P-SiC layer

Figure 9.22. XTEM image of diamond film deposited on Si using 0.3%CH4/H2, showing the presence of a 50 A-thick P-SiC layer at the interface [203],...

It is of most intrigue that unlike previous nucleation models, this model assumes a formation of diamond nuclei or nucleation sites inside the P-SiC layer, while the p-SiC layer concurrently plays a role of basal lattice for diamond epitaxial growth like in the precedent models. The second point of intrigue is the fact that the exposure and survival of the diamond nuclei or nucleation sites are made possible by a subtle balance of etching rates of Si, P-SiC, diamond, and other forms of carbon. This is consistent with the fact that HOD films can be formed only when the substrate was pretreated by proper BEN conditions. 

Nakshima et al. have fabricated p-n junction devices by employing A1 implantation to yield a p-doped layer in n-type 6H-SiC [66]. A Pt layer on top of the p-type ohmic contact (PtSi) provided both protection and a catalytic metal contact to create a chemical gas sensor device. A response (30 and 60 mV, respectively) was obtained to both 50 ppm and 100 ppm of ammonia in nitrogen at 500°C. 

N-type regions 1 are formed in a p-type substrate 2. N-type regions 5 are formed on the n-type regions 1 and a p-type layer 4 is formed on a SiC>2 layer at regions outside the n-type regions 5. 

The cubic zincblende phase of GaN (lattice parameter of about 4.5 A) is a metastable one and observed only for heteroepitaxial layers on highly mismatched cubic substrates (OOl)-oriented, for example GaAs [11], Si [12], MgO [13] and p-SiC [14],... 

Argon or hydrogen at various amount of substance flow rate relations a (nH MTs) or P (oaf Omjs) was used as carrier gas for the MTS. The influence of temperature, amount of substance flow rate relation a or P and residence time t was also investigated. The experimental identification of the reaction components is required to formulate a reaction mechanism and to compare with thermodynamic calculated gasphase composition. Knowledge of the individual running reactions should make the specific influence on the deposition of SiC layers possible. 

Nanocrystalline cubic SiC (P-SiC) films were grown on silicon (100) substrate by catalytic chemical vapor deposition (Cat-CVD) at a temperature as low as 300°C with a pre-carbonization process. To enhance nucleation density of P-SiC, a buffer layer was made by carbonizing the substrate surface. From the comparison between both carbonized sample and non-carbonized sample, the precarbonization process has beneficial effects on the growth of nanociystalline p-SiC films. Mechanistic interpretations are given to explain the carbonization process and catalyzing deposition process. 

In Figure 10.8, reference spectra of AES and XPS-EELS from various materials observed by Stoner et al. [2] are shown. Based on these data, it is clearly seen that the specimen spectra of Figure 10.7 exhibit a transition process from P-SiC formed by CVD to diamond. This transition process was also confirmed by Raman spectroscopy. According to an XTEM observation for the specimen after a 1-h biasing followed by a 5-h diamond CVD, an a-SiC layer of 6-nm (maximum 10-nm) thickness was present between the Si substrate surface and the diamond layer. An HRTEM indicated that diamonds nucleated within the interfacial layer but above the Si substrate. From the observed data, a model of diamond nucleation by BEN was proposed, as shown in Figure 10.9. 

In Refs. [253-255], BEN experiments were done by ECR plasma CVD under conditions shown in Table H.2. The substrate was a heteroepitaxial p-SiC(lOO) layer of 0.5-pm thickness deposited on Si [256] by low pressure CVD (LPCVD). Like in... 

The atomic structure of HOD film surface was investigated using electron microbeam diffraction in Ref. [259]. The substrate used was a 500-nm thick P-SiC(lOO) that had been heteroepitaxially grown on Si(lOO) and was tilted about the [1 lOj-axis by 4° from the exact (100) orientation. The thickness of the HOD film was -20 pm. According to the RHEED pattern, using the electron micro-beam (the spatial resolution as observed by SEM was 0.1 pm), the length of the surface dimer rows was 1.5nm, which was significantly shorter than that of the homoepitaxial layer, 7 to 10 nm. 

In Refs. [303-305], the interface structure was also investigated by cross-sectional HRTEM. The diamond films were grown by the three-step process, and the conditions are listed in Table H.3. Consequently, an HOD film was grown in the center of the Si(lOO) substrate. In the carburization step, there was an a-C film of 250-nm thickness on Si, in which p-SiC, diamond, and graphite were embedded. A closer examination indicated that there existed an interlayer of 1.5- to 2-pm thickness between Si and the a-C layer, which was identified as a-SiC [305]. Since the bias voltage is not usually applied uniformly across the Si wafer, the distribution of these materials depended on the location on the Si substrate. Near the edge of the... 

In Ref [315], HOD films were grown using the two-step process based on the BEN technique of Ref [289], and the interface structure was studied by TEM. As a consequence of the BEN process, (i) the carburization of Si created nanocrystalline, heteroepitaxially oriented fi-SiC, (ii) the [3-SiC layer formed nanometer size hillocks and ridges that were aligned parallel to the Si[110] direction, (hi) diamonds nucleated on the 3-SiC layer that was convex, and (iv) P-SiC existed only under the... 

This pyrocarbon layer has a high density ranging from 1.85 to 2.0 g-cin 3 and its thickness is 40 10 p,m. It can not only protect the outer SiC layer from detrimenta reactions but also protect the buffer layer and the U02 kernel from chlorine intmsion during the CVD SiC process with CH3SiCl3 as the reactant gas. 

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