Doklady Physics最新文献

This work presents a dual-gate Al_0.23Ga_0.77N/GaN MOSHEMT biosensor for the simultaneous detection of two significant CEA and HER2 cancer biomarkers. The proposed device employs two independently functionalized gate electrodes which enabling parallel sensing through a shared two-dimensional electron gas (2DEG) channel. The gates are laterally positioned and electrically separated by a 50 nm Al₂O₃ isolation gap which facilitates selective and multiplexed biomarker detection on a single platform. A bilayer dielectric stack of HfO₂ and Al₂O₃ is utilized to minimize gate leakage current and enhance sensing capability. The device performance is analysed using Silvaco ATLAS TCAD simulations with appropriate polarization based physical models. The simulation results show that the CEA-functionalized gate exhibits a sensitivity of 1.06 × 10^–6 A/µm per unit concentration. The biosensor achieves a sensitivity of 2.95 × 10^–7 A/µm per unit concentration at a drain voltage of 10 V during simultaneous detection of HER2 and CEA. The proposed structure enables efficient multiplexed biomarker sensing on a single chip and demonstrates improved performance over traditional single gate HEMT biosensors.

The development of sustainable nanomaterials with tunable electrical and dielectric properties is essential for next-generation electronic and functional device applications. In this work, mixed-phase iron oxide nanoclusters (Fe₃O₄/FeO) were synthesized via a green co-precipitation route using jojoba oil as a natural reducing and stabilizing agent under mild and environmentally friendly conditions. Structural characterization by FTIR, XRD, and SEM/EDX confirmed the formation of Fe–O bonds, organic surface capping, and the coexistence of magnetite (Fe₃O₄) and wüstite (FeO) phases. The synthesized nanoclusters exhibited nanoscale crystallinity and aggregated spherical morphology. Electrical investigations revealed two distinct frequency-dependent conduction mechanisms: localized hopping conduction at low frequencies and thermally activated variable-range hopping at higher frequencies. The activation energy increased progressively with frequency, indicating enhanced charge transport barriers at elevated frequencies. Dielectric measurements demonstrated pronounced temperature- and frequency-dependent behavior, with enhanced polarization and increased capacitance at higher temperatures. The observed electrical transport and dielectric characteristics highlight the suitability of the synthesized Fe₃O₄/FeO nanoclusters for dielectric, electronic, and charge-storage-related applications. These findings demonstrate that jojoba oil provides an effective and sustainable route for producing functional iron oxide nanomaterials with promising electrical performance.

This work investigates the impact of lateral scaling on the high-frequency characteristics of a β-Ga₂O₃ back-barrier (BB) HEMT incorporating a compositionally graded InAlN buffer. The proposed device structure consists of a sapphire substrate, graded InAlN buffer, β-Ga₂O₃ BB, GaN channel, and AlGaN barrier layer. The influence of L_G and L_GS on carrier confinement, electrical performance, and RF characteristics is systematically analysed. Energy band analysis reveals the formation of a deep quantum well at the heterointerface, facilitating strong 2DEG. The β-Ga₂O₃ BB effectively suppresses electron leakage toward the buffer region, while the graded InAlN buffer improves carrier transport through reduced scattering. The device exhibits a maximum drain current of approximately 2.4 A/mm at ({{V}_{{GS}}} = 2) V for L_G = 20 nm and a peak transconductance of about 1.55 S/mm. High-frequency analysis demonstrates a maximum f_T of nearly 300 GHz for optimized L_GS and 250 GHz for L_G = 20 nm. Furthermore, reduced gate length significantly lowers parasitic capacitances, leading to enhanced RF performance. The results indicate that lateral scaling strongly influences carrier transport, electrostatic control, and frequency response, with gate-length scaling exhibiting a more pronounced effect than source-to-gate spacing variation. The proposed β-Ga₂O₃ back-barrier architecture with a graded InAlN buffer demonstrates considerable potential for microwave, millimeter-wave, and advanced RF applications.

This paper explores the application of Organic Thin-Film Transistors (OTFTs) sensors in their detection of tumor cells, with a specific focus on measuring Prostate-Specific Antigen (PSA) concentration, a critical biomarker for diagnose of prostate-cancer. The study emphasizes the importance of sensitivity and specificity in the OTFT sensor’s compare to digital rectal examination (DRE) performance, as these parameters are essential for accurate cancer diagnostics. Sensitivity ensures that the sensor can detect low PSA concentrations, which is crucial for early-stage detection, while specificity minimizes false positives, distinguishing between malignant and benign conditions effectively.

The input characteristics of the OTFT sensor, particularly the gate voltage, play a significant role in its ability to detect PSA. Proper calibration of the gate voltage enhances the sensor’s sensitivity, enabling the detection of subtle changes in PSA levels. The output-characteristics, represented by the drain current, provide a quantifiable measure of PSA concentration, which is essential for assessing the presence and progression of tumour cells. This study demonstrates the potential of OTFT sensors as a non-invasive, precise, and reliable method for early cancer detection. By optimizing sensitivity, specificity, and the sensor’s input–output characteristics, OTFT technology could significantly improve diagnostic accuracy and patient outcomes in cancer care.

This study presents a high-performance dielectric-modulated Negative Capacitance Gate-All-Around Tunnel Field-Effect Transistor (DM-NC-GAA-TFET) biosensor for label-free biomolecule detection. The proposed device employs a nanocavity structure with varying dielectric constants (K) of biomolecules to improve sensing performance through enhanced gate-to-channel coupling and electrostatic control. The electrical and sensing characteristics of the biosensor are analyzed for different dielectric constants and cavity lengths. The transfer characteristics exhibit excellent switching behavior with an ON-state current of approximately 6.2 × 10⁻⁶ A and an OFF-state current of nearly 10⁻¹⁴ A, resulting in a high I_ON/I_OFF ratio. The output characteristics demonstrate stable current saturation and improved channel controllability, while the transconductance reaches approximately 13.5 × 10⁻⁶ S, indicating efficient carrier transport. The effect of dielectric modulation is investigated for dielectric constants ranging from 1 to 10. The drain current increases from 5.8 × 10⁻⁶ to 6.7 × 10⁻⁶ A with increasing dielectric constant, confirming enhanced sensing capability. The proposed biosensor achieves a maximum drain current sensitivity of 8.1 × 10⁻⁷ A at K = 10. Furthermore, the subthreshold swing improves from 0.066 to 0.049 V/dec, while drain induced barrier lowering (DIBL) decreases from 0.038 to 0.021. The threshold voltage sensitivity increases from 0.085 to 0.148 for a 25 nm cavity length. These results demonstrate that the proposed DM-NC-GAA-TFET biosensor provides high sensitivity, excellent switching performance, and improved electrostatic characteristics for future low-power biosensing applications.

Statistical investigation of the dynamics of cosh Gaussian (ChG) breather propagating in a cubic quintic (CQ) nonlinear medium possessing an axial hump shaped profile of quintic nonlinearity has been presented. Using moment theory approach the propagation dynamics of the breather has been reduced to an ordinary differential equation governing the evolution of the beam width of the laser beam. This allows a detailed analysis of how the beam shape parameter affects the stability and dynamical structure of the propagation dynamics of the breather. A variety of statistical and geometrical diagnostic techniques including probability density distributions, covariance matrices, recurrence structures and autocorrelation analysis are employed to investigate the underlying dynamics of the breather states. The analysis reveals that variations in the beam shape parameter of the ChG laser beam significantly modify dynamics of the breather. In particular, the transition from weak to strong nonlinear dynamics accompanied by enhanced statistical correlations and recurrence patterns has been observed.

This paper present a unified theoretical framework connecting relativistic time dilation, time–state correlation, and quantum superposition. The physical state of an object is modeled as an objective, continuous time-series function s = f(t). In the unobserved regime, the proper timeline of an object is independent of the observer’s reference frame; during observation, relativistic time dilation induces a corresponding state dilation effect, and the observed value represents the projection of the intrinsic state onto the observer’s timeline. Under elementary observation, classical behavior corresponds to a one-to-one state mapping (1 ≤ n < 2), while quantum behavior arises from a many-to-one relation (n ≥ 2) accompanied by state superposition, probabilistic outcomes, and the loss of temporal order. This paper derive formal superposition-projection formulas for time and state and apply the framework to interpret the double-slit interference experiment. The observed randomness of photon detection originates from unit-time projective sampling rather than fundamental indeterminacy, while the photon maintains a deterministic intrinsic wave function along its proper timeline. This paper predict a stepwise increase in discrete observable states as particle velocity approaches critical relativistic thresholds, supporting a continuous transition from classical to quantum behavior. This framework establishes a consistent bridge between special relativity, classical mechanics, probability theory, and quantum mechanics.

In this work, vacuum electron acceleration driven by a periodic chirped Hermite–Sinh–Gaussian (HSG) laser pulse is theoretically investigated, with particular emphasis on the influence of frequency chirp parameters and beam waist on relativistic energy gain. The study demonstrates that frequency chirping significantly modifies the phase evolution of the electromagnetic field, thereby improving phase synchronism between the electron and the accelerating field. In the unchirped case, energy saturation occurs at 3.38 GeV due to rapid electron–laser dephasing. Introduction of a positive chirp enhances phase matching and prolongs the effective interaction time, leading to systematic energy enhancement. The saturation energy increases from 3.84 GeV (α = 0.002) to 4.18 GeV (α = 0.005). Similarly, the chirp modulation constant Ω plays a crucial role in dynamic frequency compensation, increasing the maximum energy to 4.18 GeV for Ω = 0.002. Furthermore, the beam waist is found to strongly influence acceleration efficiency. Larger beam waists reduce transverse ponderomotive effects, extend the interaction length, and enhance longitudinal confinement, resulting in a monotonic rise in energy up to 5.26 GeV. The results establish chirp parameters and beam waist as effective control parameters for optimizing vacuum electron acceleration.

Silver bismuth selenide thin films were prepared and examined to understand their structural, optical, compositional, electrical, and thermoelectric behavior. X-ray diffraction analysis verified the formation of a phase pure hexagonal structure with good crystallinity and preferred orientation. The scanning electron images reveal a dense and continuous film composed of uniformly distributed nanoscale crystallites, with sizes ranging approximately 18–25 nm. Optical characterization showed strong absorption across the visible to near-infrared spectral region, and the optical band gap determined from Tauc plots lies within a range favorable for optoelectronic and energy-conversion applications. Electrical transport measurements revealed temperature dependent semiconducting behavior. Thermoelectric investigations conducted over the temperature range of 300–525 K exhibited a negative Seebeck coefficient throughout, indicating n-type charge transport. The Seebeck coefficient increased from 80.46 μV K^–1 at 300 K to 105.49 μV K^–1 at 525 K. With increasing temperature, the carrier concentration rose from 1.1 × 10¹⁹ to 1.9 × 10¹⁹ cm^–3, while the carrier mobility improved from 0.3 to 0.9 cm² V^–1 s^–1. The enhancement in mobility is attributed to the weakening of grain-boundary potential barriers at elevated temperatures. The corresponding fill factor was 0.48, resulting in a photoelectrochemical conversion efficiency of approximately 1.02%.

This study focuses on the intricate design and comprehensive investigation of electrostatic properties, analog analysis, and linearity characteristics associated with various neutral biomolecules. These investigations were conducted under varying dielectric constants, utilizing a novel device designated as the Negative Capacitance Junctionless Gate-All-Around (NC-JL-GAA) MOSFET. To evaluate the device’s sensing behavior, the analysis incorporated several neutral biomolecules, including Deoxyribonucleic Acid (DNA), Amino-propyl-tri-ethoxysilane (APTES), Streptavidin, Biotin, and air. The sensitivity of the electrostatic characteristics was thoroughly examined to ascertain the extent of their responsiveness. The simulated results demonstrate that the Subthreshold Swing (SS), Drain-Induced Barrier Lowering (DIBL), and OFF-state current (I_OFF) consistently exhibit optimal performance across all investigated conditions. Notably, DNA yielded the highest ON-current (I_ON) and I_ON/I_OFF ratio, thereby highlighting its superior interaction with the channel potential. These simulations were performed using the ATLAS™ 3D device simulator (SILVACO), which was calibrated against a device previously reported by other research groups. For validation purposes, the electrical and sensing characteristics of the device were benchmarked against those of other reported FET-based biosensors.