Anisotropy in fracture of single crystal silicon film characterized under uniaxial tensile condition

Fracture toughness testing of nanocrystalline alumina and fused quartz using chevron-notched microbeams

“…[16,32] the prenotch was machined straight down in the central part of the sample only, leaving two side walls that formed a precrack when bend-testing thin film samples of silicon oxide, nitride or oxynitride. Testing of small-scale beams containing FIB-premachined notches has been shown in several studies to give K c values near those found for macroscopic samples [15][16][17]26,27]; however, in many other studies, different results, ranging from values slightly to much higher [11,18,19,[21][22][23][24]30,33], or in some cases lower [20,34], than the toughness data from tests on macroscopic specimens of the same material were obtained with FIB-notched specimens.…”

“…The radii of the resulting notch roots range from a few tens to several hundreds of nanometres (e.g. [11,[14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31]). Beyond the need to produce a notch of sufficient sharpness, another difficulty with ion milling lies in producing a uniform notch depth and/or width: for this reason, in Refs.…”

Mechanical Properties of Silicon Microstructures

“…Thus, Chen and Leipold [195] measured the fracture toughness of single-crystal silicon using the controlled surface fracture method, and reported the values of 0.82, 0.90 and 0.95 Mpam 1/2 for the {111}, {110} and {100} orientations, respectively (Table 9.20). Later, Li et al [197] used a uniaxial tensile test with single-edge-notched tension specimen (Figure 9.16) and the following formula to estimate K Ic as a function of fracture tensile stress, σ f , notch length a, and the geometry of the specimen:…”

“…Nonetheless, this experiment completely confirmed the anisotropy of fracture toughness in microscale single-crystal silicon observed earlier. Moreover, Li et al [197] also demonstrated an anisotropy of the fracture path in single-crystal silicon, where cracks propagate predominantly on {111} and {110} low index 60 90 Orientation angle planes. At the same time they have shown that fracture paths never occur on the (001) cleavage plane.…”

“…According to this criterion the crack velocity asymptotically reaches an upper bound that is equal to the Rayleigh wave velocity c R , the velocity of acoustic surface waves. The continuum mechanical approach, however, implies the consideration of only the specific case of a crack [197] Uniaxial tensile test 2.00 {111} fracture plane [198] Double cantilever beam 0.62 [193] Double cantilever beam 0.617 [195] {112} Indentation/four-point bend 0.82 [199] Notched/four-point bend 1.34À2.85 [185] {110} Double cantilever beam 0.93 [196] {110} Indentation/four-point bend 1.18 [191] {110} Vickers indentation fracture 1.14…”