Chapter C Fig. 4.2: Crooss-sectionaal views of 90° wedge indentationns on the MSQ/Si systeem using F F FIB: (a) no interfacial crack; c (b) - (d) interfaccial crack prropagation. [1] By examining e t FIB crosss-sectionall view* (Figgs.4.2 and 4.3) and the FESEM the p plane view (Figs.4.4 annd 4.5) imaages of the wedge imppressions, thhe pop-in ev vent can b easily ideentified andd associatedd to a central crack alonng the wedgge tip (Figs.4 be 4.4a and 4.5b). In addition, thee initiationn of interfaacial crack is found tto occur att a load s somewhat h higher than that for thee pop-in. Fo or instance,, in the casee of the 90° wedge i indentation, , the pop-inn occurs at mN on the t P-h curvve (Fig.4.1((a)) but theere is no i interfacial c crack in the FIB crosss-sectional view (Fig 4.2(a), crooss-sectioned d at the * See Appenndix A for thhe schematic diagram of FIB cuttiing on wedgge indentatiion iimpression. 67 Chapter C m middle of thhe wedge im mpression), and the FE ESEM planee view (Fig.4.4(a)) sho ows only a central craack at this looad. Fig. 4.3: Crross-sectionnal views of F o 120° wedge indentaations on thhe MSQ/Sii system u using FIB: (a) ( no interffacial crack; (b) – (d) in nterfacial crrack propaggation. [1] 68 . a t e of the 90 ( a)) but th e o ss-sectione d g e indentat i C hapter 4 67 em using FESEM v ent can 4 .4a and t a load ° wedge e re is no d at the i on m a F u m iddle of. interfa c s s-sectiona l a ges of the d to a centra n of interf a e pop-in. F o 2 mN on t s s-sectional ic diagram indentatio n c ial crack p r l view * (Fi g wedge im p l crack alo n a cial crack o r. instance , t he P-h cur v view (Fig . of FIB cutt i n s on the M r opagation. g s.4 .2 and 4 p ressions, t h n g the wed g is found t , in the cas e v e (Fig.4.1 ( . 4 .2( a), cr o i ng on wed g C SQ/Si