Ultrafast Photoacoustic Nanometrology of InAs Nanowires Mechanical Properties

InAs nanowires are emerging as go-to materials in avariety of applications ranging from optoelectronics to nano-electronics, yet a consensus on their mechanical properties is stilllacking. The mechanical properties of wurtzite InAs nanowires arehere investigated via a multitechnique approach, exploitingelectron microscopies, ultrafast photoacoustics, andfinite elementsimulations. A benchmarked elastic matrix is provided and a Youngmodulus of 97 GPa is obtained, thus clarifying the debated issue ofInAs NW elastic properties. The validity of the analyticalapproaches and approximations commonly adopted to retrievethe elastic properties from ultrafast spectroscopies is discussed.The mechanism triggering the oscillations is unveiled. Nanowireoscillations in this system arise from a sudden expansion of the supporting substrate rather than the nanowire itself. This mechanismconstitutes a new paradigm, being at variance with respect to the excitation mechanisms so far identified in ultrafast experiments onnanowires and on a plethora of nanosystems. The presentfindings are relevant in view of applications involving InAs nanowires,knowledge of their mechanical properties being crucial for any device engineering beyond a trial-and-error approach. The resultsbear generality beyond the specific case, the launching mechanism potentially encompassing a variety of systems serving as nano-optomechanical resonators.