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Direct Nanoscale Characterization of Deep Levels in AgCuInGaSe 2 Using Electron Energy‐Loss Spectroscopy in the Scanning Transmission Electron Microscope
Author(s) -
Deitz Julia I.,
Paul Pran K.,
Farshchi Rouin,
Poplavskyy Dmitry,
Bailey Jeff,
Arehart Aaron R.,
McComb David W.,
Grassman Tyler J.
Publication year - 2019
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201901612
Subject(s) - scanning transmission electron microscopy , materials science , electron energy loss spectroscopy , spectroscopy , semiconductor , scanning electron microscope , characterization (materials science) , deep level transient spectroscopy , band gap , electron , transmission electron microscopy , nanoscopic scale , high resolution transmission electron microscopy , optoelectronics , analytical chemistry (journal) , nanotechnology , silicon , chemistry , physics , chromatography , quantum mechanics , composite material
Abstract A new experimental framework for the characterization of defects in semiconductors is demonstrated. Through the direct, energy‐resolved correlation of three analytical techniques spanning six orders of magnitude in spatial resolution, a critical mid‐bandgap electronic trap level ( E V + 0.56 eV) within Ag 0.2 Cu 0.8 In 1− x Ga x Se 2 is traced to its nanoscale physical location and chemical source. This is achieved through a stepwise, site‐specific correlated characterization workflow consisting of device‐scale (≈1 mm 2 ) deep level transient spectroscopy (DLTS) to survey the traps present, scanning probe–based DLTS (scanning‐DLTS) for mesoscale‐resolved (hundreds of nanometers) mapping of the target trap state's spatial distribution, and scanning transmission electron microscope based electron energy‐loss spectroscopy (STEM‐EELS) and X‐ray energy‐dispersive spectroscopy for nanoscale energy‐, structure, and chemical‐resolved investigation of the defect source. This first demonstration of the direct observation of sub‐bandgap defect levels via STEM‐EELS, combined with the DLTS methods, provides strong evidence that the long‐suspected Cu In/Ga substitutional defects are indeed the most likely source of the E V + 0.56 eV trap state and serves as a key example of this approach for the fundamental identification of defects within semiconductors, in general.