The Role of Long‐Wave Bending Vibrations in the Destruction of Ultrathin Al Films

Abstract

The molecular dynamics method is used to study the process of development of dynamic instability of a thin film, leading to its destruction. The calculations are performed for a thin aluminum film using the interatomic interaction potential tested by comparing the numerical results with the analytical ones from the elasticity theory. An original approach which allows one to calculate the dispersion law of long‐wave phonons in ultrathin films is developed. The temperatures (<600 K) at which the system remains stable for 0.6 ns are found. This makes it possible to analyze the low‐frequency part of the spectrum down to the minimum frequency νmin = 0.0166 THz, and to determine the vibration frequency of the longest bending wave ν0 = 0.033 THz which decreases with increasing temperature, and therefore, its period grows. Once the vibration period becomes comparable with the time of simulation, there occurs a continuous increase in the amplitude of this mode which will be referred to as “retarded mode.” It is shown that the film destruction begins with the attainment of a certain critical value of the bending wave amplitude.