Limits...
Valence band offset of wurtzite InN/SrTiO3 heterojunction measured by x-ray photoelectron spectroscopy.

Li Z, Zhang B, Wang J, Liu J, Liu X, Yang S, Zhu Q, Wang Z - Nanoscale Res Lett (2011)

Bottom Line: The valence band offset (VBO) of wurtzite indium nitride/strontium titanate (InN/SrTiO3) heterojunction has been directly measured by x-ray photoelectron spectroscopy.The VBO is determined to be 1.26 ± 0.23 eV and the conduction band offset is deduced to be 1.30 ± 0.23 eV, indicating the heterojunction has a type-I band alignment.The accurate determination of the valence and conduction band offsets paves a way to the applications of integrating InN with the functional oxide SrTiO3.

View Article: PubMed Central - HTML - PubMed

Affiliation: Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P,O, Box 912, Beijing 100083, People's Republic of China. lizhiwei@semi.ac.cn.

ABSTRACT
The valence band offset (VBO) of wurtzite indium nitride/strontium titanate (InN/SrTiO3) heterojunction has been directly measured by x-ray photoelectron spectroscopy. The VBO is determined to be 1.26 ± 0.23 eV and the conduction band offset is deduced to be 1.30 ± 0.23 eV, indicating the heterojunction has a type-I band alignment. The accurate determination of the valence and conduction band offsets paves a way to the applications of integrating InN with the functional oxide SrTiO3.

No MeSH data available.


Spectra of InN/STO sample. 3d core level peaks for the InN and thin InN/SrTiO3 heterojunction samples, Ti 2p core level peaks for the SrTiO3 and InN/SrTiO3 heterojunction samples, and valence band photoemission for the InN and SrTiO3 samples. All peaks have been fitted using a Shirley background and Voigt (mixed Lorentzian-Gaussian) line shapes.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3211249&req=5

Figure 1: Spectra of InN/STO sample. 3d core level peaks for the InN and thin InN/SrTiO3 heterojunction samples, Ti 2p core level peaks for the SrTiO3 and InN/SrTiO3 heterojunction samples, and valence band photoemission for the InN and SrTiO3 samples. All peaks have been fitted using a Shirley background and Voigt (mixed Lorentzian-Gaussian) line shapes.

Mentions: Figure 1 shows all the CL spectra including In 3d peak recorded on InN thick film and InN/STO samples, Ti 2p spectrum on bulk STO and InN/STO samples, as well as VB spectra recorded on InN and bulk STO samples. The CL spectra were fitted to Voigt (mixed Lorentzian-Gaussian) line shape by employing a Shirley background. The In 4d and Ti 3p semicore-level peaks used by other researchers [13,14] in similar experiments have not been chosen in the analysis as these levels are located at very low binding energy and hybridized with other shallow levels easily which will limit the accuracy of the results attained using these levels. Since considerable accordance of the fitted line to the original measured data has been obtained, the uncertainty of the CL position should be lower than 0.03 eV, as evaluated by numerous fitting with different parameters. The main uncertainty comes from the difficulty in determining the value of the VBM exactly. The peak parameters and the VBM positions are listed in Table 1 for clarity. In Figure 1 (InN), the In 3d spectrum include two peaks: 3d5/2 (443.50 eV) and 3d3/2 (451.09 eV) peaks, which are separated by the spin-orbit interaction with a splitting energy of 7.57 eV. With careful Voigt fitting, it was found out that both of the peaks consist of two components. The first In 3d5/2 component located at 443.50 eV is attributed to the In-N bonding [15], and the second, at 444.52 eV, is identified as being due to surface contamination. This two-peak profile of the In 3d5/2 spectra in InN is so typical and have been demonstrated by other researchers [16-20]. Comparing their binding energy separation with previous results [19,21,22], we suggest to assign the second peak at 444.52 eV to the In-O bonding which is due to contamination by oxygen during the growth process. The ratio of In-N peak intensity to the oxygen-related peak indicates that only a small quantity of oxygen contamination exists in our samples. The Ti 2p spectrum (STO in Figure 1) also consists of two components: 2p3/2 (458.19 eV) and 2p1/2 (464.09 eV) peaks. Both of them are quite symmetric indicating the uniform bonding state and good quality of our sample. Using the linear extrapolation method mentioned above, the VBM of InN and STO are 0.45 ± 0.1 eV and 1.91 ± 0.1 eV, respectively. The spectra of InN/STO sample are shown in Figure 1 (InN/STO). Compared with the spectra recorded on the InN and STO samples, the In 3d core level is shifted to 443.68 eV and Ti 2p is shifted to 458.17 eV. The VBO value is calculated to be 1.26 ± 0.23 eV by substituting those values into Eq. (1).


Valence band offset of wurtzite InN/SrTiO3 heterojunction measured by x-ray photoelectron spectroscopy.

Li Z, Zhang B, Wang J, Liu J, Liu X, Yang S, Zhu Q, Wang Z - Nanoscale Res Lett (2011)

Spectra of InN/STO sample. 3d core level peaks for the InN and thin InN/SrTiO3 heterojunction samples, Ti 2p core level peaks for the SrTiO3 and InN/SrTiO3 heterojunction samples, and valence band photoemission for the InN and SrTiO3 samples. All peaks have been fitted using a Shirley background and Voigt (mixed Lorentzian-Gaussian) line shapes.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211249&req=5

Figure 1: Spectra of InN/STO sample. 3d core level peaks for the InN and thin InN/SrTiO3 heterojunction samples, Ti 2p core level peaks for the SrTiO3 and InN/SrTiO3 heterojunction samples, and valence band photoemission for the InN and SrTiO3 samples. All peaks have been fitted using a Shirley background and Voigt (mixed Lorentzian-Gaussian) line shapes.
Mentions: Figure 1 shows all the CL spectra including In 3d peak recorded on InN thick film and InN/STO samples, Ti 2p spectrum on bulk STO and InN/STO samples, as well as VB spectra recorded on InN and bulk STO samples. The CL spectra were fitted to Voigt (mixed Lorentzian-Gaussian) line shape by employing a Shirley background. The In 4d and Ti 3p semicore-level peaks used by other researchers [13,14] in similar experiments have not been chosen in the analysis as these levels are located at very low binding energy and hybridized with other shallow levels easily which will limit the accuracy of the results attained using these levels. Since considerable accordance of the fitted line to the original measured data has been obtained, the uncertainty of the CL position should be lower than 0.03 eV, as evaluated by numerous fitting with different parameters. The main uncertainty comes from the difficulty in determining the value of the VBM exactly. The peak parameters and the VBM positions are listed in Table 1 for clarity. In Figure 1 (InN), the In 3d spectrum include two peaks: 3d5/2 (443.50 eV) and 3d3/2 (451.09 eV) peaks, which are separated by the spin-orbit interaction with a splitting energy of 7.57 eV. With careful Voigt fitting, it was found out that both of the peaks consist of two components. The first In 3d5/2 component located at 443.50 eV is attributed to the In-N bonding [15], and the second, at 444.52 eV, is identified as being due to surface contamination. This two-peak profile of the In 3d5/2 spectra in InN is so typical and have been demonstrated by other researchers [16-20]. Comparing their binding energy separation with previous results [19,21,22], we suggest to assign the second peak at 444.52 eV to the In-O bonding which is due to contamination by oxygen during the growth process. The ratio of In-N peak intensity to the oxygen-related peak indicates that only a small quantity of oxygen contamination exists in our samples. The Ti 2p spectrum (STO in Figure 1) also consists of two components: 2p3/2 (458.19 eV) and 2p1/2 (464.09 eV) peaks. Both of them are quite symmetric indicating the uniform bonding state and good quality of our sample. Using the linear extrapolation method mentioned above, the VBM of InN and STO are 0.45 ± 0.1 eV and 1.91 ± 0.1 eV, respectively. The spectra of InN/STO sample are shown in Figure 1 (InN/STO). Compared with the spectra recorded on the InN and STO samples, the In 3d core level is shifted to 443.68 eV and Ti 2p is shifted to 458.17 eV. The VBO value is calculated to be 1.26 ± 0.23 eV by substituting those values into Eq. (1).

Bottom Line: The valence band offset (VBO) of wurtzite indium nitride/strontium titanate (InN/SrTiO3) heterojunction has been directly measured by x-ray photoelectron spectroscopy.The VBO is determined to be 1.26 ± 0.23 eV and the conduction band offset is deduced to be 1.30 ± 0.23 eV, indicating the heterojunction has a type-I band alignment.The accurate determination of the valence and conduction band offsets paves a way to the applications of integrating InN with the functional oxide SrTiO3.

View Article: PubMed Central - HTML - PubMed

Affiliation: Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P,O, Box 912, Beijing 100083, People's Republic of China. lizhiwei@semi.ac.cn.

ABSTRACT
The valence band offset (VBO) of wurtzite indium nitride/strontium titanate (InN/SrTiO3) heterojunction has been directly measured by x-ray photoelectron spectroscopy. The VBO is determined to be 1.26 ± 0.23 eV and the conduction band offset is deduced to be 1.30 ± 0.23 eV, indicating the heterojunction has a type-I band alignment. The accurate determination of the valence and conduction band offsets paves a way to the applications of integrating InN with the functional oxide SrTiO3.

No MeSH data available.