SPM Characterization of Pulsed Laser Deposited Nanocrystalline CrN Hard Coatings

Abstract

Nanocrystalline CrN coatings, widely required for surface engineering application covering wear and corrosion resistance, need to be investigated for atomic scale morphology, surface roughness, local stiffness, phase uniformity, and homogeneity. Evolution of these properties as a function of thickness need to be studied. In this paper, we have attempted to address these issues through use of a multimode scanning probe microscope (SPM) equipped to carry out Atomic Force Microscopy (AFM) and Atomic Force Acoustic microscopy (AFAM) of Chromium nitride films (100-500 nm thick) on Si prepared under high vacuum by pulsed Laser Ablation using Nd-YAG Q-switched laser. Prior to SPM analysis, the coatings were annealed in N2 atmosphere at 700 degrees C for 30 minutes for improving crystallanity and coating substrate adhesion. The GIXRD patterns of these annealed specimens showed formation of nanocrystalline CrN. Also signature of amorphous phases was seen. The grain size was estimated to be less than 30 nm. Contact mode AFM imaging revealed a roughness value less than 50 nm. Local stiffness values were calculated from AFM force-distance curves. Imaging of frictional force and surface flaws are being investigated by Frictional Force Microscopy (FFM), resonance spectroscopy, and AFAM, respectively. The contrast in AFAM images is seen due to variation in surface elasticity in reference and CrN samples. Stiffness constant and elastic modulus were calculated for both the samples and compared.

Electrochemical and adhesion properties of hydrothermally deposited nano-ZrO2 coatings on oxide layers of stainless steel

“…It appears from AFAM images of ZPLD sample, certain fraction of ultrafine ZrO 2 nano-particles get entrapped in grain boundaries during the growth process. This entrapment adds to hardening of grain boundaries [19]. This behavior is not observed in ZPOH and ZPOO samples, where growth of ZrO 2 coating is limited due to the unfavorable substrate surfaces.…”

“…Pre-oxidized SS specimens and the ZrO 2 coated samples have been subsequently characterized by different techniques like scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) to understand surface morphologies, oxide structures and chemical states. The qualitative nano-mechanical properties and adhesion force of the ZrO 2 coating with the substrate surface have been evaluated by atomic force acoustic microscopy (AFAM), a special mode of scanning probe microscopy and force-distance (FD) spectroscopy [19]. The corrosion resistance properties of the ZrO 2 coated samples have been studied by potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS).…”

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

“…Coupled modes of vibration specic to surface elasto-mechanical response are measured and a spatial elasticity map is eventually generated. 25,26,35,36 In our study, presence of particulates ($micrometers) restricts spatial elasticity mapping with accuracy so we carried out the AFAM study by mapping with magnitude of the coupled oscillation. Point spectroscopy technique was used to determine the relative stiffness of at surface and particulate with respect to Si (111).…”

“…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…”

“…This AFAM formalism is used to discriminate hard and so regions. 36 Mag image of Fig. 9(a) for DLC-100 specimen illustrates an elasticity contrast, where the soer regions are dark and the stiffer regions are bright.…”