Direct Evaluation of the Quantum Confinement Effect in Single Isolated Ge Nanocrystals

Abstract

To address the yet open question regarding the nature of quantum confinement in Ge nanocrystals (Ge NCs) we employed scanning tunneling spectroscopy to monitor the electronic structure of individual isolated Ge NCs as a function of their size. The (single-particle) band gaps extracted from the tunneling spectra increase monotonically with decreasing nanocrystal size, irrespective of the capping ligands, manifesting the effect of quantum confinement. Band-gap widening of ∼1 eV with respect to the bulk value was observed for Ge-NCs 3 nm in diameter. The picture emerging from comparison with theoretical calculations and other experimental results is discussed.

Dense Ge nanocrystals embedded in TiO2 with exponentially increased photoconduction by field effect

“…For sample Sasd the absorption limit E g is 0.73 eV, while for S550 the absorption threshold is about 1.14 eV in good agreement with the threshold of the spectral photocurrent as shown further. This blue-shift of the bandgap for Ge NCs in respect to bulk Ge can be explained by quantum confinement in NCs with diameter of about 5 nm in agreement with HRTEM and XRD results 26 , 27 . In comparison to our results on films with 60% Ge, smaller optical bandgap of about 0.7 eV was reported for smaller Ge content of only 33% in films deposited at 600 °C by sputtering from alloy GeTiO 2 target 35 .…”

Solid‐State Route for the Synthesis of Scalable, Luminescent Silicon and Germanium Nanocrystals

“…The NCs showed PL in near‐IR region ca. 1320 nm (Figure A), indicating an estimated optical band gap of 0.95 eV, which is in good agreement with recent calculations . The PLE spectrum showed peak maximum ca.…”

Voltammetry investigation on copper zinc tin sulphide /selenide (CZTSxSe1-x) alloy nanocrystals: Estimation of composition dependent band edge parameters

“…To implement this idea, however valance band (E VB ) and conduction band (E CB ) edges of CZTS x Se 1 À x alloy nanocrystals need to be estimated as a function of 'x'. These parameters in case of quantum dots are generally estimated by ultraviolet photoelectron spectroscopy (UPS) [22] and scanning tunneling spectroscopy(STS) [23,24]. Both these techniques involve major instrumentation and tedious sample preparation and thus out of reach to many chemists for the routine applications.…”