Characterization of Films with Thickness Less than 10 nm by Sensitivity-Enhanced Atomic Force Acoustic Microscopy

Abstract

We present a method for characterizing ultrathin films using sensitivity-enhanced atomic force acoustic microscopy, where a concentrated-mass cantilever having a flat tip was used as a sensitive oscillator. Evaluation was aimed at 6-nm-thick and 10-nm-thick diamond-like carbon (DLC) films deposited, using different methods, on a hard disk for the effective Young's modulus defined as E/(1 - ν2), where E is the Young's modulus, and ν is the Poisson's ratio. The resonant frequency of the cantilever was affected not only by the film's elasticity but also by the substrate even at an indentation depth of about 0.6 nm. The substrate effect was removed by employing a theoretical formula on the indentation of a layered half-space, together with a hard disk without DLC coating. The moduli of the 6-nm-thick and 10-nm-thick DLC films were 392 and 345 GPa, respectively. The error analysis showed the standard deviation less than 5% in the moduli.

Nano scale investigation of particulate contribution to diamond like carbon film by pulsed laser deposition

“…The purpose of this study is to determine surface elastic forces on at surface and particulate region of DLC lms. The expression for stiffness (K*) of the coupled oscillator system can be written as; 25,26,35,36,51…”

“…The contact resonance frequency of Si with known elastic constants and Poisson ratio was measured prior to commencing the measurements on the DLC specimens for contact resonance frequency and relative stiffness values. Mathematical expression for the contact resonance frequency the coupled oscillator system is given by eqn (4), 25,26,35,36,51…”

Mechanical characterization of porous nano-thin films by use of atomic force acoustic microscopy

“…Hurley et al used the CR-FM method to study the adhesion at an interface of a 20 nm thin film of gold and silicon substrate [38]. Muraoka applied cantilevers modified with point weights to characterize 10 nm thin diamond-like-carbon layers by use of the AFAM method [39]. The AFAM method was also used to determine the indentation modulus of silicon oxide films with thicknesses ranging from 8 nm to 28 nm [40].…”

“…The AFAM method was also used to determine the indentation modulus of silicon oxide films with thicknesses ranging from 8 nm to 28 nm [40]. In the studies presented in [39,40] the substrate influence was considered. The results presented in this paper were obtained by combining the ability of the AFAM method to characterize very thin film [40] with that to determine the indentation modulus of low and ultra-low k materials as reported in [41,42,43].…”

Local elasticity and mobility of twin boundaries in martensitic films studied by atomic force acoustic microscopy

“…AFAM combines ultrasonics with atomic force microscopy (AFM) [11][12][13][14]. It allows one to measure the local contact stiffness k * and with appropriate contact mechanics the local elasticity of samples on nanometer scales [14][15][16][17][18]. Longitudinal waves supplied by a waveform generator are injected into the sample making its surface vibrate and excite the cantilever beam to bending modes.…”