Operando Surface Characterization of InP Nanowire p–n Junctions

Abstract

We present an in-depth analysis of the surface band alignment and local potential distribution of InP nanowires containing a p–n junction using scanning probe and photoelectron microscopy techniques. The depletion region is localized to a 15 nm thin surface region by scanning tunneling spectroscopy and an electronic shift of up to 0.5 eV between the n- and p-doped nanowire segments was observed and confirmed by Kelvin probe force microscopy. Scanning photoelectron microscopy then allowed us to measure the intrinsic chemical shift of the In 3d, In 4d, and P 2p core level spectra along the nanowire and the effect of operating the nanowire diode in forward and reverse bias on these shifts. Thanks to the high-resolution techniques utilized, we observe fluctuations in the potential and chemical energy of the surface along the nanowire in great detail, exposing the sensitive nature of nanodevices to small scale structural variations.

Boosting the performance of NO2 gas sensors based on n–n type mesoporous ZnO@In2O3 heterojunction nanowires: in situ conducting probe atomic force microscopic elucidation of room temperature local electron transport

“…By moving the conducting probe towards the material, a biased potential difference is generated owing to the variation in the Fermi energies between the probe and the material. 50 The local charge transport mechanism during NO 2 gas sensing was further probed by monitoring the surface potential or contact potential difference (CPD) mapping of the n–n type heterojunction nanowires using SKPM during exposure to the NO 2 gas environment as shown in Scheme 2 . The work function, ( φ ) of a MOS is defined as the quantity of energy needed to move an electron present in the surface of the semiconductor material to the vacuum level.…”

Direct observation of surface charge redistribution in active nanoscale conducting channels by Kelvin Probe Force Microscopy

“…Furthermore, the operational status of devices can be studied by in-situ local potential extraction e.g. surface plasmon field [21], potential fluctuation in crystal grains [12,22], junction of sollar cell under illumination [23], potential change in p-n junction under biasing [7,[24][25][26], nonlinear local potential drop due to Schottky contacts [27], the variation of doping or surface charge [28]. The local electrical potential is not only associated with the properties of materials or device themselves but also with the measurement environment [29][30][31], applied bias induced local charge trapping or injection [30,[32][33][34], and ion transportation [35].…”

Atomic Hydrogen Annealing of Graphene on InAs Surfaces and Nanowires: Interface and Morphology Control for Optoelectronics and Quantum Technologies

“…InAs NWs are deposited onto the sample from the original growth substrate using a dry deposition method. 56 To transfer the graphene, we use the well-established polymer-assisted technique; 48 more details are found in the Methods and Materials section. Single/multilayer graphene is initially identified on a SiO 2 /Si wafer (highly doped Si wafers with ∼300 nm SiO 2 on top) before transferring (Figure 1b), and its thickness is estimated considering its color contrast under an optical microscope and confirmed using Raman spectroscopy 45 (Figure S4).…”

“…To remove the native oxide and other impurities, atomic hydrogen cleaning has been efficient for InAs substrate and NW surfaces. Thus, samples can be introduced to a UHV chamber and native oxides removed using hydrogen cleaning. ,, Hydrogen gas was introduced into the preparation chamber through a leak valve ( P ∼ 5 × 10 –6 mbar) and thermally cracked at around 1700 °C to atomic hydrogen (H*) . Samples were annealed at 400 °C in parallel for full cleaning and to remove hydrocarbons and oxides.…”