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To increase the storage capacity of hard disk drives, Heat-Assisted Magnetic Recording (HAMR) takes advantage of laser heating to temporarily reduce the coercivity of recording media, enabling the writing of very small data bits on materials with high thermal stability. One key challenge in implementing HAMR is effective thermal management, which requires reliable determination of the thermal properties of HAMR materials over their range of operating temperature. This work reports the thermal properties of dielectric (amorphous silica, amorphous alumina, and AlN), metallic (gold and copper), and magnetic alloy (NiFe and CoFe) thin films used in HAMR heads from room temperature to 500 K measured with time-domain thermoreflectance. Our results show that the thermal conductivities of amorphous silica and alumina films increase with temperature, following the typical trends for amorphous materials. The polycrystalline AlN film exhibits weak thermal anisotropy, and its in-plane and through-plane thermal conductivities decrease with temperature. The measured thermal conductivities of AlN are significantly lower than that which would be present in single-crystal bulk material, and this is attributed to enhanced phonon-boundary scattering and phonon-defect scattering. The gold, copper, NiFe, and CoFe films show little temperature dependence in their thermal conductivities over the same temperature range. The measured thermal conductivities of gold and copper films are explained by the diffuse electron-boundary scattering using an empirical model. 

Exploration and advancements in ultrawide bandgap (UWBG) semiconductors are pivotal for next-generation high-power electronics and deep-ultraviolet (DUV) optoelectronics. Here, we used a thin heterostructure design to facilitate high conductivity due to the low electron mass and relatively weak electron-phonon coupling, while the atomically thin films ensured high transparency. We used a heterostructure comprising SrSnO₃/La:SrSnO₃/GdScO₃(110), and applied electrostatic gating, which allow us to effectively separate charge carriers in SrSnO₃from dopants and achieve phonon-limited transport behavior in strain-stabilized tetragonal SrSnO₃. This led to a modulation of carrier density from 10¹⁸to 10²⁰cm⁻³, with room temperature mobilities ranging from 40 to 140 cm²V⁻¹s⁻¹. The phonon-limited mobility, calculated from first principles, closely matched experimental results, suggesting that room temperature mobility could be further increased with higher electron density. In addition, the sample exhibited 85% optical transparency at a 300-nm wavelength. These findings highlight the potential of heterostructure design for transparent UWBG semiconductor applications, especially in DUV regime. 

The use of magnetic tunnel junction (MTJ)-based devices constitutes an important basis of modern spintronics. However, the switching layer of an MTJ is widely believed to be an unmodifiable setup, instead of a user-defined option, posing a restriction to the function of spintronic devices. In this study, we realized a reliable electrical control of the switching layer in perpendicular MTJs with 0.1 nm Ir dusting. Specifically, a voltage pulse with a higher amplitude drives the magnetization switching of the MTJ's bottom electrode, while a lower voltage amplitude switches its top electrode. We discussed the origin of this controllability and excluded the possibility of back-hopping. Given the established studies on enhancing the voltage-controlled magnetic anisotropy effect by adopting Ir, we attribute this switching behavior to the significant diffusion of Ir atoms into the top electrode, which is supported by scanning transmission electron microscopy with atomic resolution. 

Abstract Rich electron-matter interactions fundamentally enable electron probe studies of materials such as scanning transmission electron microscopy (STEM). Inelastic interactions often result in structural modifications of the material, ultimately limiting the quality of electron probe measurements. However, atomistic mechanisms of inelastic-scattering-driven transformations are difficult to characterize. Here, we report direct visualization of radiolysis-driven restructuring of rutile TiO₂under electron beam irradiation. Using annular dark field imaging and electron energy-loss spectroscopy signals, STEM probes revealed the progressive filling of atomically sharp nanometer-wide cracks with striking atomic resolution detail. STEM probes of varying beam energy and precisely controlled electron dose were found to constructively restructure rutile TiO₂according to a quantified radiolytic mechanism. Based on direct experimental observation, a “two-step rolling” model of mobile octahedral building blocks enabling radiolysis-driven atomic migration is introduced. Such controlled electron beam-induced radiolytic restructuring can be used to engineer novel nanostructures atom-by-atom. 

As an ultrawide bandgap (∼4.1 eV) semiconductor, single crystalline SrSnO3 (SSO) has promising electrical properties for applications in power electronics and transparent conductors. The device performance can be limited by heat dissipation issues. However, a systematic study detailing its thermal transport properties remains elusive. This work studies the temperature-dependent thermal properties of a single crystalline SSO thin film prepared with hybrid molecular beam epitaxy. By combining time-domain thermoreflectance and Debye–Callaway modeling, physical insight into thermal transport mechanisms is provided. At room temperature, the 350-nm SSO film has a thermal conductivity of 4.4 W m−1 K−1, ∼60% lower than those of other perovskite oxides (SrTiO3, BaSnO3) with the same ABO3 structural formula. This difference is attributed to the low zone-boundary frequency of SSO, resulting from its distorted orthorhombic structure with tilted octahedra. At high temperatures, the thermal conductivity of SSO decreases with temperature following a ∼T−0.54 dependence, weaker than the typical T−1 trend dominated by the Umklapp scattering. This work not only reveals the fundamental mechanisms of thermal transport in single crystalline SSO but also sheds light on the thermal design and optimization of SSO-based electronic applications. 

Abstract Understanding the kinetics of interfacial reaction in the deposition of metal contacts on 2D materials is important for determining the level of contact tenability and the nature of the contact itself. Here, we find that some metals, when deposited onto layered black-arsenic films using e-beam evaporation, form a-few-nm thick distinct intermetallic layer and significantly change the nature of the metal contact. In the case of nickel, the intermetallic layer is Ni 11 As 8 , whereas in the cases of chromium and titanium they are CrAs and a-Ti 3 As, respectively, with their unique structural and electronic properties. We also find that temperature, which affects interatomic diffusion and interfacial reaction kinetics, can be used to control the thickness and crystallinity of the interfacial layer. In the field effect transistors with black-arsenic channel, due to the specifics of its formation, this interfacial layer introduces a second and more efficient edge-type charge transfer pathway from the metal into the black-arsenic. Such tunable interfacial metal contacts could provide new pathways for engineering highly efficient devices and device architectures. 

The oxides of platinum group metals are promising for future electronics and spintronics due to the delicate interplay of spin-orbit coupling and electron correlation energies. However, their synthesis as thin films remains challenging due to their low vapour pressures and low oxidation potentials. Here we show how epitaxial strain can be used as a control knob to enhance metal oxidation. Using Ir as an example, we demonstrate the use of epitaxial strain in engineering its oxidation chemistry, enabling phase-pure Ir or IrO2 films despite using identical growth conditions. The observations are explained using a density-functional-theory-based modified formation enthalpy framework, which highlights the important role of metal-substrate epitaxial strain in governing the oxide formation enthalpy. We also validate the generality of this principle by demonstrating epitaxial strain effect on Ru oxidation. The IrO2 films studied in our work further revealed quantum oscillations, attesting to the excellent film quality. The epitaxial strain approach we present could enable growth of oxide films of hard-to-oxidize elements using strain engineering. 

Unidirectional spin Hall magnetoresistance (USMR) is a magnetoresistance effect with potential applications to read two-terminal spin–orbit-torque (SOT) devices directly. In this work, we observed a large USMR value (up to 0.7 × 10 −11 per A/cm 2 , 50% larger than reported values from heavy metals) in sputtered amorphous PtSn 4 /CoFeB bilayers. Ta/CoFeB bilayers with interfacial MgO insertion layers are deposited as control samples. The control experiments show that increasing the interfacial resistance can increase the USMR value, which is the case in PtSn 4 /CoFeB bilayers. The observation of a large USMR value in an amorphous spin–orbit-torque material has provided an alternative pathway for USMR application in two-terminal SOT devices.