AlN Passivation Layer-Mediated Improvement in Tensile Failure of Flexible ZnO:Al Thin Films

Abstract

AlN passivation layer-mediated improvement in tensile failure of ZnO:Al thin films on polyethersulfone substrates is investigated. ZnO:Al films without any passivation layer were brittle with a crack-initiating bending strain εc of only about 1.13% with a saturated crack density ρs of 0.10 μm(-1) and a fracture energy Γ of 49.6 J m(-2). On passivation by an AlN overlayer, the fracture energy of the system increased considerably and a corresponding improvement in εc was observed. AlN layers deposited at higher discharge powers yielded higher fracture energy and exhibited better performance in terms of εc and ρs.

Enhanced Fracture Resistance of Flexible ZnO:Al Thin Films in Situ Sputtered on Bent Polymer Substrates

“…[1][2][3] Nevertheless, the brittleness of inorganic thin films often results in failure of the flexible electronic devices even at low applied strains during stretching, folding and bending. [3][4][5][6] For example, crack-initiating critical strains of inorganic thin film materials such as In 2 O 3 :Sn (ITO), AlN, GaAs and Al 2 O 3 were as low as 1.1 %, 1.4 %, 0.3 % and 0.48 %, respectively. 1,[4][5][6][7] A larger critical strain value indicates a higher crack initiation resistance in the films.…”

“…[3][4][5][6] For example, crack-initiating critical strains of inorganic thin film materials such as In 2 O 3 :Sn (ITO), AlN, GaAs and Al 2 O 3 were as low as 1.1 %, 1.4 %, 0.3 % and 0.48 %, respectively. 1,[4][5][6][7] A larger critical strain value indicates a higher crack initiation resistance in the films.…”

“…The level of tensile strain was changed by adjusting the bending radius of the PES substrate. The pre-tensile strain, ε p , applied to the substrate was calculated using the relationship between the film/substrate thicknesses and the bending radius as given by 5, 6,8 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 …”

Temperature-Dependent Fatigue Failure of Flexible Poly(9,9-dioctylfluorene-alt-benzothiadiazole) (PFBT)–ZnO Nanoparticle Hybrid Resistive Switching Memory Devices

“…ZnO NPs are homogeneously inserted in the PFBT matrix as electron acceptors to form conductive paths (see Figure a). , When the device is subjected to repetitive bending, the accumulated film stresses cause two types of cracks in the functional layer, denoted as A and B (see Figure b). Crack A directly initiates at the polymer surface when the applied strain reaches the critical strain ε c1 , and then irregularly propagates due to the high stress concentration around the crack tip (right inset in Figure b). Meanwhile, the NPs on the surface are the preferential sites for crack B initiation due to the elastic mismatch between the NPs and polymer (see left inset in Figure b). , Crack B propagates along the polymer/NP interface and terminates at the bottom of the NP, and it will continue to expand only when the applied strain achieves the critical strain ε c2 .…”

Mechanical properties of amorphous indium–gallium–zinc oxide thin films on compliant substrates for flexible optoelectronic devices

“…However, transparent conducting oxide films are brittle by nature, and susceptible to cracking and/or buckling delamination under externally applied mechanical deformation, which significantly limits the flexibility of the devices [7]. Consequently, failure behaviour of the films under various loading modes such as stretching, bending, or twisting becomes a critical issue during both manufacturing processes and in service conditions [8]. Hence, this gives rise to the motivation for predicting the onset of failure such as critical strain and critical radius of curvature to provide this information to optoelectronic device designers.…”