Determination of the elastic modulusof nanostructures with sizes at several nm range is a challenge. Inthis study, we designed an experiment to measure the elastic modulusof amorphous Al2O3films with thicknesses varyingbetween 2 and 25 nm. The amorphous Al2O3wasin the form of a shell, wrapped around GaAs nanowires, thereby formingan effective core/shell structure. The GaAs core comprised a singlecrystal structure with a diameter of 100 nm. Combined in situ compressiontransmission electron microscopy and finite element analysis wereused to evaluate the elastic modulus of the overall core/shell nanowires.A core/shell model was applied to deconvolute the elastic modulusof the Al2O3shell from the core. The resultsindicate that the elastic modulus of amorphous Al2O3increases significantly when the thickness of the layer issmaller than 5 nm. This novel nanoscale material can be attributedto the reconstruction of the bonding at the surface of the material,coupled with the increase of the surface-to-volume ratio with nanoscaledimensions. Moreover, the experimental technique and analysis methodspresented in this study may be extended to measure the elastic modulusof other materials with dimensions of just several nanometers. [ABSTRACT FROM AUTHOR]