Controlling the heat transport and thermal conductivity through a material is of prime importance for thermoelectric applications. Phononic crystals, which are a nanostructured array of specially designed pores, can suppress heat transportation owing to the phonon wave interference, resulting in bandgap formation in their band structure. To control heat phonon propagation in thermoelectric devices, phononic crystals with a bandgap in the THz regime are desirable. In this study, we carried out simulation on snowflake shaped phononic crystal and obtained several phononic bandgaps in the THz regime, with the highest being at ≈2 THz. The phononic bandgap position and the width of the bandgap were found to be tunable by varying the neck-length of the snowflake structure. A unique bandgap map computed by varying the neck-length continuously provides enormous amounts of information as to the size and position of the phononic bandgap for various pore dimensions. We have also carried out transmission spectrum analysis and found good agreement with the band structure calculations. The pressure map visualized at various frequencies validates the effectiveness of snowflake shaped nano-pores in suppressing the phonons partially or completely, depending on the transmission probabilities.

Graphene-based thermal rectification was investigated by measuring the thermal transport properties of asymmetric suspended graphene nanomesh devices. A sub-10 nm periodic nanopore phononic crystal structure was successfully patterned on the half area of the suspended graphene ribbon by helium ion beam milling technology. The ‘differential thermal leakage’ method was developed for thermal transport measurement without disturbance from the leakage of electron current through the suspended graphene bridge. A thermal rectification ratio of up to 60% was observed in a typical device with a nanopore pitch of 20 nm. By increasing the nanopore pitch in a particular range, the thermal rectification ratio showed an increment. However, this ratio was degraded by increasing the environmental temperature. This experiment suggests a promising way to develop a high-performance thermal rectifier by using a phononic crystal to introduce asymmetry on homogeneous material.

This paper demonstrates that the electrical properties of suspended graphene nanomesh (GNM) can be tuned by systematically changing the porosity with helium ion beam milling (HIBM). The porosity of the GNM is well-controlled by defining the pitch of the periodic nanopores. The defective region surrounding the individual nanopores after HIBM, which limits the minimum pitch achievable between nanopores for a certain dose, is investigated and reported. The exponential relationship between the thermal activation energy (E_A) and the porosity is found in the GNM devices. Good E_A tuneability observed from the GNMs provides a new approach to the transport gap engineering beyond the conventional nanoribbon method.

While the importance of atomic-scale features in silicon-based device for quantum application has been recognized and even the placement of a single atom is now feasible, the role of a dopant in the substrate has not attracted much attention in the context of quantum technology. In this paper, we report random telegraph signals (RTSs) originated from trapping and detrapping of an electron by a donor in the substrate of a p-type metal–oxide–semiconductor field-effect-transistor. RTSs, not seen when the substrate was grounded, were observed when a positive bias was applied to the substrate. The comprehensive study on the signals observed reveals that the nature of the RTSs is discrete threshold voltage variations due to the change in the depletion layer width depending on the charge state of a single dopant, neutral or positively charged.

The need for hardware random number generators (HRNGs) that can be integrated in a silicon (Si) complementary-metal–oxide–semiconductor (CMOS) platform has become increasingly important in the era of the Internet-of-Things (IoT). Si MOSFETs exhibiting random telegraph signals (RTSs) have been considered as such a candidate for HRNG, though its application has been hindered by RTS’s variability and uncontrollable, unpredictable characteristics. In this paper, we report the generation and randomness evaluation of random numbers from RTSs in a Si single electron pump (SEP) device at room temperature. SEP devices are known to consistently produce RTSs due to a quantum dot electrically defined by multi-layer polycrystalline Si gates. Using RTSs observed in our devices, random numbers were extracted by a classifier supported by supervised learning, where part of data was used to train the classifier before it is applied to the rest to generate random numbers. The random numbers generated from RTSs were used as inputs for the Monte Carlo method to calculate the values of π, and the distribution was compared against the result obtained from the Mersenne Twister, a representative pseudo-random number generator (PRNG), under the same condition. π was estimated more than 80 000 times, and the distribution of the estimated values has a central value of 3.14 with a variance of 0.273, which is only twice as large as the result from PRNG. Our result paves a way to fully electronic CMOS compatible HRNGs that can be integrated in a modern system-on-a-chip in IoT devices.

In the post-Moore era, advanced nanoscale thermal management relies primarily on the precise engineering of phonons. In this context, interfaces at critical junctions—especially between key functional materials—have emerged as a fundamental bottleneck. With the growing prominence of 2D materials as vital components for thermal diodes, their interfaces with 3D substrates increasingly represent a critical factor that determines the overall functionality of the device. However, dynamic thermal transport at such interfaces remains unquantified, constrained by complex interaction potentials, intrinsic limits of molecular simulations, and the spatiotemporal gap between atomistic simulations and realistic device dimensions. In this work, by leveraging the complementary strengths of direct and reverse non-equilibrium molecular dynamics, we successfully demonstrate and quantify significant interfacial thermal rectification driven by temperature-dependent phonon spectral mismatch. To accurately reflect realistic interfacial interactions at 2D/3D contacts, a hybrid interatomic potential framework was implemented. This work not only clarifies the microscopic origins of directional heat transport across heterogeneous junctions but also highlights contact engineering as a promising strategy for future thermal logic devices.