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

Abstract

Polymer–nanoparticle (NP) hybrid nanocomposites act as essential elements for ultraflexible memory devices due to their processability, flexibility, and chemical resistance. However, a key limitation to their potential is associated with their mechanical reliability with the variation of temperature, which is still poorly understood. Herein, we systematically investigated the temperature-dependent fatigue failure of the Al/poly­(9,9-dioctylfluorene-alt-benzothiadiazole)–ZnO/Al/PET device, in which an 80% reduction in the fatigue lifetime of the device was observed as the temperature decreased from 40 to −40 °C. The finite element analysis results and theoretical calculations indicated that polymer/NP interfaces play different roles in crack propagations at different temperatures. At relatively high temperature, the elastic mismatch at the polymer/NP interface allows it to alleviate the crack propagation encountered with repetitive mechanical stress. However, this behavior is suppressed by the significant decrease of the polymer critical strain induced by the segmental motion in the polymer backbone at low temperature. In this case, large stiffness mismatch at the polymer/NP interface accelerates the crack propagation, which will inhibit electron transfer and eventually lead to device breakdown. This study may pave the way for future realization of ultraflexible hybrid memory devices utilized in harsh environments.

Effect of Interfacial Modification on the Low-Temperature Fatigue Properties of Polymer/MXene Flexible Pressure Sensors

“…Moreover, the subzero temperature mechanical properties of multiwalled carbon nanotube-reinforced epoxy nanocomposites were reported by Chen et al With the temperature decreasing from room temperature to −196 °C, plasticization of the epoxy matrix and swelling-induced interfacial stresses lead to a deteriorated mechanical performance . Similarly, we previously investigated the temperature-dependent fatigue properties of the Al/poly­(9,9-dioctylfluorene-altbenzothiadiazole)–ZnO/Al/PET resistive device and demonstrated that the poor low-temperature performance was mainly caused by the large stiffness mismatch at the polymer/NP interface …”

“…15 Similarly, we previously investigated the temperature-dependent fatigue properties of the Al/poly(9,9dioctylfluorene-altbenzothiadiazole)−ZnO/Al/PET resistive device and demonstrated that the poor low-temperature performance was mainly caused by the large stiffness mismatch at the polymer/NP interface. 16 On the other hand, previous research also showed that matrix backbones, such as polyurethane, rubber, hyperbranched polymer, and siloxane, are the other key factors that affect the fatigue characteristics of sensors based on MXene/polymer composites at subzero temperatures. 17−19 For instance, when the polydimethylsiloxane (PDMS) matrix was cooled down to −150 °C, the damage mode transitioned from microcrack damage caused by plastic squeeze slip to brittle fracture damage induced by the cleavage step under a quasistatic compression load, as proposed by Sun et al 19 Wang et al found that the neat epoxy matrix exhibited a slight nonlinear failure behavior at −196 °C, which was ascribed to the restrained mobility of the polymer chains due to the less free volume in the frozen epoxy network at cryogenic temperatures.…”

Effect of Fatigue Fracture on Resistive Switching of ZnO and NiO Stacking Films

“…Upon threshold bending cycles, the delamination between NiO and ZnO functional layers restrains the injected electrons from overflowing into the GaIn electrode. [ 33 ] Meanwhile, the severe cracks cut off the conductive paths and result in permanent device break‐down. Our work clearly indicates that the RS performance is sensitive to the fracture behavior at the p‐n interface, while proper engineering stacking structure of the active layer can enhance the mechanical endurance.…”

Temperature‐Dependent Fatigue Characterization of Flexible Cellulose Nanocrystal Strain Sensor

“…The large elastic mismatch between different layers caused remaining stress, resulting in poor sensitivity of the flexible CNC film under various temperatures. [ 29 ] Therefore, the contributions of bending and temperature to structural damage were separately deliberated. Herein, all the layers were assumed to be homogeneous in the microstructure without any impurity.…”