Nanoscale band gap spectroscopy on ZnO and GaN-based compounds with a monochromated electron microscope

Abstract

Monochromated low-loss EELS ͑electron energy-loss spectroscopy͒ is explored as an analytical technique for nanoscale mapping of the electronic band gap energy on arsenic-implanted ZnO, CdZnO, and InGaN compounds. Its accuracy is confirmed independently with Raman spectroscopy. From a ternary compound, the relationship between the band gap energy and the chemical composition is determined, a powerful application of low-loss EELS. The effects of electron beam delocalization are discussed using examples from In 0.25 Ga 0.75 N quantum wells.

Combination of electron energy-loss spectroscopy and energy dispersive x-ray spectroscopy to determine indium concentration in InGaN thin film structures

“…The adjusted R 2 (R 2 =0.9845) confirms the plasmon peak energy versus calibrated indium concentration is linear over the complete compositional range 0<x<1, with an uncertainty in the indium concentration (random mean-square error from linear regression) of x=±0.037, which indicates an improved accuracy in the determination of indium concentration of InGaN compared to previous studies [3]. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59Figure 3: dependence of plasmon peak position on measured indium concentration in InGaN, including our data as well as data from other groups [3,[25][26][27][28][29]. The black line is the linear least-squares regression fit to all data.…”

Nanoscale mapping of optical band gaps using monochromated electron energy loss spectroscopy

“…Thus, the observed EELS intensity can closely match what is observed in optical experiments, thereby allowing us to extract the optical band gap from EELS spectra with sufficient energy resolution and statistical quality [15][16][17][18][19].…”

“…Here we monitor the energy loss of a monochromatic electron beam due to excitation processes in the sample. Taking advantage of the high spatial resolution of the electron beam, mapping of the local geometries of systems and their optical response through surface plasmon polaritons and localized surface plasmons [12][13][14], and band gap excitations can be performed [15][16][17][18][19].…”

Spin-polarized Wide Electron Slabs in Functionally Graded Polar Oxide Heterostructures

“…Electron energy-loss spectroscopy (EELS) was further utilized to probe the band structure of the heterostructure using a monochrome STEM probe with a diameter of about 1 nm. The energy resolution of the measurement was better than 0.13 eV and the corrections of bandgap, composition and profiling depth are the same as discussed earlier41. Temperature-dependent Hall measurements were carried out at low magnetic field of ~1 T and temperature ranging from 10 to 300 K. Quantum transport properties were measured in a rotator-equipped Oxford refrigerator at 1.4 K with the magnetic field up to 10 T. The field-dependent Hall effect was performed at 10 K for sample A with B field up to 1.4 T. by using the Lakeshore commercial Hall effect system 7707A.…”