Doping profile of InP nanowires directly imaged by photoemission electron microscopy
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(Color online) (A) Schematic of an n-i-n-doped InP NW. (B) SE image of a native oxide covered NW showing a bright undoped segment (hν = 70 eV, kinetic energy (KE) = 0.9 eV). (C) XPEEM image using electrons from the In 4d core level of the NW (hν = 70 eV, KE = 47.3 eV). (D) Mirror mode image of an uncleaned NW. (E) Schematic energy band diagram showing the SE emission process as described in Ref. 15. The ionization energies for the two segments are equal (En = Ei ), and the vacuum level potential (Evac ) is non-uniform outside the sample. Thus, electrons from the n-type part need ΔEn more energy to reach the detector energy level (EDetector ). Ec , Ev , and EF denote the conduction band edge, valence band edge, and Fermi level, respectively. The false color code in (B, C) depicts the photoelectron intensity with increasing intensity: black-green-yellow-red in the online figure (intrinsic segment in (B) is brightest).
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(Color online) (A) SE image of a cleaned InP n-i-n-NW (hν = 133 eV, KE 0 eV). (B) Intensity profile along the marked line in (A). The dotted lines mark the two space charge regions (SCRs): The left SCR is 300 nm wide and the right SCR is 200 nm. The Au-particle can be found at the far right in the image.
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