CMOS-compatible Techniques Research Articles

Highly textured CMOS-compatible hexagonal boron nitride-based neuristor for reservoir computing

Significant advancements in artificial neural networks (ANNs) have driven the rapid progress of artificial intelligence and machine learning. While current feedforward neural networks primarily handle static data, recurrent neural networks (RNNs) are designed for dynamical systems. However, RNNs demand extensive training on specific tasks, limiting their scalability and affordability for edge computing. Physical reservoir computing (RC) offers an alternative approach by mapping inputs into high-dimensional states, allowing for pattern analysis within a fixed reservoir. Unlike RNNs, RC is well-suited for temporal and sequential data processing with rapid speed and low training costs. This makes RC suitable for hardware implementation across various research domains. Nonetheless, existing demonstrations of RC remain constrained to small-scale device arrays. As electronic synapse arrays aim to approach very large-scale and highly complex hardware as in the human brain, managing heat dissipation becomes a formidable challenge. In this work, we successfully developed the neuristors based on textured h-BN films, prepared using a CMOS-compatible technique, and constructed a physical RC system based on as-fabricated devices. Our approach leverages vertically aligned BN to provide aligned diffusion paths for the reproducible migration process of metal ions from the electrodes and offers a potential solution for thermal management in electronic devices. This achievement highlights the promising potential of our neuristors for future high-density and energy-efficient neuromorphic computing.

Fabrication of gallium nitride waveguide resonators by high-power impulse magnetron sputtering at room temperature

In this work, we demonstrate gallium nitride (GaN) waveguide resonators by sputtering amorphous GaN films on the silicon-based substrate. With the aid of high-power impulse magnetron sputtering (HiPIMS), high-quality, high-deposition-rate, and high-flatness GaN films can be deposited directly onto the silicon substrate with a 4 μm buried oxide layer at room temperature. Waveguide resonators with a quality factor of up to 4 × 104 are demonstrated, and closely critical coupling is achieved at a 0.2 μm gap by optimizing the gap sizes, showing a high extinction ratio of waveguide resonators at ≈24 dB. The fabrication process of HiPIMS-GaN waveguide resonators utilizes CMOS-compatible techniques and operates at a low thermal budget. Compared to conventional GaN films fabricated using metal-organic chemical vapor deposition, this study offers the potential to produce low-cost GaN waveguides on amorphous substrates and realize integrated GaN photonics in optical communication, nonlinear photonics, and quantum photonics by high-quality HiPIMS films.

Nanoscale biosensor with integratedthermoregulation controller for DNA diagnostics.

We present a CMOS compatible technique for fabrication a sensor system based on field-effect transistors with a nanowire channel with an integrated thermoregulation elements. The proposed system provides the necessary temperature regimes for many bioanalytical studies. Field-effect transistors with a nanowire channel were fabricated using of reactive-ion etching of the upper layer of a silicon on insulator through a mask formed by electron beam lithography. Titanium thermoresistive strips for temperature control were located on the surface of the chip nearby to the nanowire transistors. Their fabrication is carried out simultaneously with the formation of contact pads to the transistor electrodes, which made it possible to avoid additional technological steps. A demonstration of a system with a built-in temperature controller for the determination of nucleic acids was carried out on model oligonucleotides. Increasing the operating temperature of the device to the ranges at which DNA hybridization occurs most efficiently allows increasing specificity and avoiding false positive results, as well as reducing analysis time. The possibility of heating up to 85–90∘C allows you to reuse such devices.

Advances in Nanomaterials Integration in CMOS-Based Electrochemical Sensors: A Review

The monolithic integration of electrochemical sensors with instrumentation electronics on semiconductor technology is a promising approach to achieve sensor scalability, miniaturization, and increased signal-to-noise ratio. Such integration requires postprocess modification of microchips (or wafers) fabricated in standard semiconductor technology [e.g., complementary metal–oxide–semiconductor (CMOS)] to develop sensitive and selective sensing electrodes. This review focuses on the postprocess fabrication techniques for the addition of nanomaterials to the electrode surface, a key component in the construction of electrochemical sensors that has been widely used to achieve surface reactivity and sensitivity. Several CMOS-compatible techniques are summarized and discussed in this review for the deposition of nanomaterials such as gold, platinum, carbon nanotubes, polymers, and metal oxide/nitride nanoparticles. These techniques include electroless deposition, electrochemical deposition, liftoff, microspotting, dip-pen lithography, physical adsorption, self-assembly, and hydrothermal methods. Finally, this review is concluded and summarized by stating the advantages and disadvantages of these deposition methods.

Growth Mechanisms and Morphology Engineering of Atomic Layer-Deposited WS2.

Transition-metal dichalcogenides (TMDs) have attracted intense research interest for a broad range of device applications. Atomic layer deposition (ALD), a CMOS compatible technique, can enable the preparation of high-quality TMD films on 8 to 12 in. wafers for large-scale circuit integration. However, the ALD growth mechanisms are still not fully understood. In this work, we systematically investigated the growth mechanisms for WS2 and found them to be strongly affected by nucleation density and film thickness. Transmission electron microscope imaging reveals the coexistence and competition of lateral and vertical growth mechanisms at different growth stages, and the critical thicknesses for each mechanism are obtained. The in-plane lateral growth mode dominates when the film thickness remains less than 5.6 nm (8 layers), while the vertical growth mode dominates when the thickness is greater than 20 nm. From the resulting understanding of these growth mechanisms, the conditions for film deposition were optimized and a maximum grain size of 108 nm was achieved. WS2-based field-effect transistors were fabricated with electron mobility and on/off current ratio up to 3.21 cm2 V-1 s-1 and 105, respectively. Particularly, this work proves the capability of synthesis of TMD films in a wafer scale with excellent controllability of thickness and morphology, enabling many potential applications other than transistors, such as nanowire- or nanosheet-based supercapacitors, batteries, sensors, and catalysis.

α-phase PVDF MEMS cantilever excited by electrostriction and evaluated up to 160 °C in air by laser-Doppler vibrometry

The electroactive polymer polyvinylidene fluoride (PVDF) has gained much interest in smart materials research with a wide application range for industry and consumer applications due to the low cost, flexibility, chemical resistance, non-toxicity, and light weight. In this work, we present an α-phase PVDF cantilever that exploits electrostriction as the main transducer mechanism for excitation. We realize thin PVDF films with a thickness of ∼190 nm and a low roughness (∼19 nm RMS). Electrostrictive cantilevers need high electric fields to achieve amplitudes comparable to piezoelectric counterparts. At thinner films, lower voltage levels are requested for comparable electric fields, thus making electrostrictive PVDF cantilevers a viable route and subsequently allowing broader use of PVDF in MEMS devices. We use an asymmetric electrode design that has the advantage of shifting the neutral axis out of the PVDF without enhancing cantilever thickness with a supporting device layer. In addition, these devices can be produced by CMOS compatible micromachining techniques. We measured the electrostrictive and piezoelectric actuation signal with laser-Doppler vibrometry and showed the frequency spectrum and curvature of such α-phase PVDF cantilevers. The cantilevers have a curvate of up to 120 m−1 at 1500 kV/cm. We demonstrate that the electrostrictive actuation has a low temperature dependency in the range from 25 up to 130 °C. A typical cantilever exhibits a geometry dependent low spring constant (k ∼ 0.3 N m−1) and a low quality factor (Q ∼ 75) in air.

High responsivity in MoS2 phototransistors based on charge trapping HfO2 dielectrics

2D Transition Metal Dichalcogenides hold a promising potential in future optoelectronic applications due to their high photoresponsivity and tunable band structure for broadband photodetection. In imaging applications, the detection of weak light signals is crucial for creating a better contrast between bright and dark pixels in order to achieve high resolution images. The photogating effect has been previously shown to offer high light sensitivities; however, the key features required to create this as a dominating photoresponse has yet to be discussed. Here, we report high responsivity and high photogain MoS2 phototransistors based on the dual function of HfO2 as a dielectric and charge trapping layer to enhance the photogating effect. As a result, these devices offered a very large responsivity of 1.1 × 106 A W−1, a photogain >109, and a detectivity of 5.6 × 1013 Jones under low light illumination. This work offers a CMOS compatible process and technique to develop highly photosensitive phototransistors for future low-powered imaging applications.

A Sensor System Based on a Field-Effect Transistor with a Nanowire Channel for the Quantitative Determination of Thyroid-Stimulating Hormone

Here we present an original CMOS compatible technique for fabrication a sensor system based on field-effect transistors with a nanowire channel and its application for the quantitative determination of thyroid-stimulating hormone (TSH) in model blood serum. The fabrication process is based on the reactive-ion etching of the upper layer of silicon on insulator through a mask formed by electron beam lithography. The detection is based on the registration the change in the conductivity of the transistor during the selective interaction of the analyte with specific biomolecules on its surface. There were fabricated field-effect transistors with a nanowire channel of $$70{-}90\text{nm}$$ wide and $$3{-}5 \mu\text{m}$$ in long and a contact leads completely insulated from the analyte fluid. As the model antigen protein TSH of the pituitary gland, and as the recognition biomolecules - the specific to TSH fragments of antibodies were used, which were oriented immobilized on the nanowires surface. We carefully studied the conditions for biospecific interaction of antibodies with TSH. The detection limit of TSH was found to be $$1\times 10^{-4}\mu\text{IU}/\text{mL}$$ , which is significantly lower in comparison with currently used methods of standard enzyme-linked immunosorbent assay.

Dual-periodically poled lithium niobate microcavities supporting multiple coupled parametric processes.

Periodically poled lithium niobate (PPLN) microcavities with additional reciprocal vectors attract attention as a platform for efficient parametric nonlinear optical processes with wavelength and polarization flexibility. Here, we report the simultaneous realization of multiple coupled parametric processes in PPLN microdisk cavities with dual periods as a result of the significantly increased number of reciprocal vectors to fulfill quasi-phase matchings for a series of nonlinear processes. PPLN microdisks with up to 1.43×105 quality factors and unit domain size of 90 nm in width were fabricated using CMOS compatible microfabrication techniques and electrically poled with the help of piezoresponse force microscopy. The conversion efficiency of second-harmonic signal was measured to be 51%W-1. Our work paves the way towards efficient cascaded parametric effects including third- and fourth-harmonic generations.

Design and Development of Photonic Biosensors for Swine Viral Diseases Detection.

In this paper we introduce a field diagnostic device based on the combination of advanced bio-sensing and photonics technologies, to tackle emerging and endemic viruses causing swine epidemics, and consequently significant economic damage in farms. The device is based on the use of microring resonators fabricated in silicon nitride with CMOS compatible techniques. In the paper, the designed and fabricated photonic integrated circuit (PIC) sensors are presented and characterized, showing an optimized performance in terms of optical losses (30 dB per ring) and extinction ration for ring resonances (15 dB). Furthermore, the results of an experiment for porcine circovirus 2 (PCV2) detection by using the developed biosensors are presented. Positive detection for different virus concentrations has been obtained. The device is currently under development in the framework of the EU Commission co-funded project SWINOSTICS.

Integrated and Interconnected Array of Light-Emitting Transistors and Transistor Lasers on Silicon for Photonic Logic

A scalable method of integrating III-V epitaxial structures onto silicon and producing a large-area array of interconnected three-terminal photonic devices in the integrated material is demonstrated. This work establishes CMOS-compatible techniques for GaAs-based active photonic material (n-InGaP/p-GaAs/n-GaAs) to be converted into a distribution of epitaxial islands with direct thermal and electrical connection to a silicon host wafer. A temporary epitaxial bonding process orients and etches modified heterojunction bipolar transistor (HBT) material into a gridded mesh of islands (collector-side up) on a silicon-based carrier wafer with device-level alignment. A subsequent epitaxial transfer creates a permanent metal-eutectic bond between the III-V islands and the silicon host wafer that serves as a uniform electrical interconnect between front-end-of-line processed CMOS and the collector terminals of a photonic chip layer. Thermal, electrical, and mechanical characterization of the integrated material is performed to ensure that the interconnect is suitable for fabrication of photonic devices into the larger-area transferred material. A separate epitaxial process for uniting passive waveguide materials to the same host wafer is then similarly performed. The result is a closely-aligned grid where each III-V island is surrounded by passive material islands. The integrated III-V islands (emitter-side up) are then patterned in unison into an array of light-emitting transistors (LET) and edge-emitting transistor lasers (TL) that are designed for efficient optical coupling into waveguides formed in the passive material, functioning together as active and passive devices in a single network. Device processing parameters are inspected and optimized to account for variations in processing on integrated (thin-film) III-V materials as compared to monolithic device processing, as well as to adhere to CMOS-compatible methods and metallization. The resulting array of three-terminal photonic devices are linked by means of a vertical electrical interconnect through the collector contact and a lateral optical interconnect aligned to the carrier-recombination quantum well (QW) in the base region. Optical and electrical testing (DC) is performed on the integrated devices both individually and as an integrated network for electrical and optical output characteristics, while a comparison to fabricated monolithic three-terminal photonic devices is utilized to relate performance of integrated active photonic devices. Initial work on high-speed testing is performed to benchmark the thermal and electrical improvements in integrated photonic devices. Simulation of the device characteristics is further employed to investigate methods to optimize optical output in relation to electrical gain and beta suppression. The techniques and processes established enable a scalable network of photonic devices for novel heterogeneously integrated electronic-photonic circuitry. This heterogeneous integration produces a platform for pairing a photonic chip layer with a CMOS host wafer such that the interconnects for electrical and optical signals allow for photonic logic designs. Figure 1

Filament Assisted Chemical Vapor Deposited organosilicate as chemical layer for nanometric hydrocarbon gas sensors

The fabrication of gravimetric gas sensors based on Nano Electro Mechanical System (NEMS) requires the use of a chemical sensitive layer that is uniformly deposited by a solvent-free deposition technique. In this work, we show than an organosilicate layer deposited by Filament-Assisted Chemical Vapor Deposition using methyltriethoxysilane presents very high affinity toward hydrocarbon gas. High partition coefficients toward toluene and pentane were obtained on Quartz Crystal Microbalance sensors after being annealed at 400 °C. It is shown that the hydrophobic nature of this material composed of a SiOSi backbone with methyl groups bonded to silicon, combined with the presence of isolated ethoxy groups and microporosity, allow a very high sensibility in comparison to others SiOCH. Furthermore, the functionalization of NEMS-based gas sensors was demonstrated. This material, deposited using a CMOS compatible technique, constitutes a promising solution for the development of a complete and portable multi-gas analysis system.

Electrochemcial Synthesis of Nanoporous Hematite (α-Fe2O3) and Their Applications Towards Photocatalytic Water Oxidation

The capture and storage of solar energy in the molecular bonds of chemical fuels provides a promising route to overcoming the current global energy dependence on fossil fuels. Solar assisted water splitting, the process usually known as artificial photosynthesis, is a favourable means of converting solar energy into transportable and end user chemical fuels. The system requires optimisation in terms of cost and performance on a scale commensurate with the global energy demand. However, most abundant semiconductors suffer from the undesirable photoelectron-hole recombination within the semiconductor due to their short diffusion path lengths and lifetimes, which results in fewer than 10% of the incident photons being used for water splitting. Hematite (α-Fe2O3), one of the few naturally occurring n-type metal oxides, is the most promising candidate for an efficient photoanode because of its high earth abundance (4th most abundant element in the earth’s crust) and visible light active band gap of 2.1 eV, a scalable CMOS compatible synthesis technique, excellent photostability and favourable energy band position capable to drive off the water oxidation reactions without of any external bias. Despite having those advantages, hematite has several inherent drawbacks such as poor electron mobility (~ 10-1 cm2 V-1 s-1)[1], short excited carrier lifetime (about 10 ps)[2] and short carrier (hole) diffusion length (2−4 nm)[3]. Hence, most of the photogenerated charge carriers (electron-hole) cannot be extracted to the semiconductor-electrolyte interface before they quickly recombine inside of the materials and dissipate as heat energy. Nanoscale design of hematite such as nanowires[4], cauliflowers[5] or core-shell nanostructures synthesised via solution based hydrothermal growth and expensive chemical vapour deposition or atomic layer deposition[6] along with surface modification with oxygen evolution catalysts[5] have led to circumvent their drawbacks and made the nanostructured hematite a promising photoanode. In this work, electrochemical deposition of nanoporous α-Fe2O3 and surface modification with cobalt (Co) catalyst is described. The method involves the electrodeposition of iron (Fe) nanoporous film followed by thermal annealing in air (Fig. 1a). The kinetics of the photoelectrochemical (PEC) reactions was improved by modifying the hematite surface with oxygen evolution catalysts. The PEC activity of the optimised nanoporous α-Fe2O3/Co has been correlated with the morphology, thickness and Co loading under standard operational conditions (Am 1.5 G, 100 mW/cm2, 1 mol/L KOH). This presentation will also discuss our current research to develop cheap and efficient photocatalysts towards fabrication of tandem PEC water splitting device. Figure. SEM images of the electrodeposited nanoporous hematite (α-Fe2O3) in (a) low and (b) high magnified view. Acknowledgements: Authors acknowledge Marie Curie Actions co-funded Irish Research Council Elevate fellowship ELEVATEPD/2014/15.

A High-PDE, Backside-Illuminated SPAD in 65/40-nm 3D IC CMOS Pixel With Cascoded Passive Quenching and Active Recharge

We present a complete pixel based on a single-photon avalanche diode (SPAD) fabricated in a backside-illuminated (BSI) 3D IC technology. The chip stack comprises an image sensing tier produced in a 65-nm image sensor technology and a data processing tier in 40-nm CMOS. Using a simple, CMOS-compatible technique, the pixel is capable of passive quenching and active recharge at voltages well above those imposed by a single transistor whilst ensuring that the reliability limits across the gate-source ( $\text {V} _{\text {GS}}$ ), gate-drain ( $\text {V} _{\text {GD}}$ ) and drain–source ( $\text {V} _{\text {DS}}$ ) are not exceeded for any device. For a given technology, the circuit extends the maximum excess bias that SPADs can be operated at when using transistors as quenching elements, thus improving the SPAD sensitivity, timing performance, and photon detection probability uniformity. Implemented with 2.5-V thick oxide transistors and operated at 4.4-V excess bias, the design achieves a timing jitter of 95-ps full-width at half maximum, maximum photon detection efficiency (PDE) of 21.9% at 660 nm and 0.08% afterpulsing probability with a dead time of 8 ns. This is both the lowest afterpulsing probability at 8-ns dead time and the highest peak PDE for a BSI SPAD in a 3D IC technology to date.

Single-electron tunneling through an individual arsenic dopant in silicon.

We report the single-electron tunneling behaviour of a silicon nanobridge where the effective island is a single As dopant atom. The device is a gated silicon nanobridge with a thickness and width of ∼20 nm, fabricated from a commercially available silicon-on-insulator wafer, which was first doped with As atoms and then patterned using a unique CMOS-compatible technique. Transport measurements reveal characteristic Coulomb diamonds whose size decreases with gate voltage. Such a dependence indicates that the island of the single-electron transistor created is an individual arsenic dopant atom embedded in the silicon lattice between the source and drain electrodes, and furthermore, can be explained by the increase of the localisation region of the electron wavefunction when the higher energy levels of the dopant As atom become occupied. The charge stability diagram of the device shows features which can be attributed to adjacent dopants, localised in the nanobridge, acting as charge traps. From the measured device transport, we have evaluated the tunnel barrier properties and obtained characteristic device capacitances. The fabrication, control and understanding of such "single-atom" devices marks a further step towards the implementation of single-atom electronics.

Dispersion of nonresonant third-order nonlinearities in GeSiSn ternary alloys.

Silicon (Si), tin (Sn), and germanium (Ge) alloys have attracted research attention as direct band gap semiconductors with applications in electronics and optoelectronics. In particular, GeSn field effect transistors can exhibit very high performance in terms of power reduction and operating speed because of the high electron drift mobility, while the SiGeSn system can be constructed using CMOS-compatible techniques to realize lasers, LED, and photodetectors. The wide Si, Ge and Sn transparencies allow the use of binary and ternary alloys extended to mid-IR wavelengths, where nonlinearities can also be employed. However, neither theoretical or experimental predictions of nonlinear features in SiGeSn alloys are reported in the literature. For the first time, a rigorous and detailed physical investigation is presented to estimate the two photon absorption (TPA) coefficient and the Kerr refractive index for the SiGeSn alloy up to 12 μm. The TPA spectrum, the effective TPA wavelength cut-off, and the Kerr nonlinear refractive index have been determined as a function of alloy compositions. The promising results achieved can pave the way to the demonstration of on-chip nonlinear-based applications, including mid-IR spectrometer-on-a-chip, all-optical wavelength down/up-conversion, frequency comb generation, quantum-correlated photon-pair source generation and supercontinuum source creation, as well as Raman lasing.

Electrochemical Deposition of Cu2O Thin Film As Efficient Photocatalyst for Water Splitting Reaction

Solar water splitting can form the basis of a sustainable hydrogen based energy economy, however the system requires optimisation in terms of cost and performance on a scale commensurate with the global energy demand. Photocatalysts consist of solar spectrum absorber semiconductor materials and co-catalysts as the redox mediator for hydrogen and oxygen evolution reactions. The key factors for efficient solar water splitting process to occur with such photocatalysts are a semiconductor with a sufficiently narrow band gap to absorb visible lights, a suitable thermodynamic potential for the redox reactions, and stability against photocorrosion. However, current photocatalysts also suffer from undesirable photoelectron-hole (charge carrier) recombination within the semiconductor due to their short diffusion path lengths and lifetimes, which results in fewer than 10% of the incident photons being used for water splitting. Cuprous Oxide (Cu2O), one of the few naturally occurring p-type metal oxides, is the most promising candidate for an efficient photocathode because of its earth abundance, a band gap of 2.0 eV, which enables efficient visible light absorption, a scalable CMOS compatible deposition technique (e.g., electrodeposition), and favourable energy band position i.e. conduction band lies 0.7 eV negative of the hydrogen evolution potential that drives off half of the water reduction reaction without of any external bias. However, the application of Cu2O as photocathode is limited by two drawbacks; fast photoelectron–hole recombination owing to short carrier diffusion length and self-photo corrosion in aqueous solution under illumination since the potentials of Cu2O reduction and oxidation to metallic Cu and CuO, respectively, lie within the bandgap. Hence, the solar-to-fuel conversion efficiency on Cu2O depends on how fast the photoelectron can be extracted to the reduction reaction sites and inhibition of electrolyte access to Cu2O surface. A thin protective coating and a heterostructure in the seed layer of the electrochemically deposited Cu2O film enhance the overall photocatalytic performance versus the Cu2O film alone. The thickness of the Cu2O film was optimised to avoid the charge carrier recombination towards the efficient and stable photocatalytic performance. The photocatalytic performance of Cu2O thin film is shown in Fig 1, in which the film performance is unexpectedly high and only dropped to 22% after the first cycle at 0.0 VRHE, after which it stabilises. This presentation will discuss our current research to develop cheap and efficient photocatalysts and their enhancement mechanism towards photocatalytic water splitting reactions. Figure 1

Experimental realization of perfect terahertz plasmonic absorbers using highly doped silicon substrate and CMOS-compatible techniques

We experimentally demonstrate that at terahertz frequencies perfect plasmonic absorbers made on a highly doped silicon platform can be easily realized, exhibiting near-zero dips in the reflection spectra. The unit cell of the absorber consists of a dielectric layer of SiO2 film sandwiched between a highly doped silicon wafer and the copper structures, in the form of either one-dimensional stripe array or two-dimensional cross array. The reflection spectrum of the proposed absorbers are characterized using a terahertz time-domain spectroscopy system and the experimental results are in good agreement with numerical simulations. The dependence of the absorption on the THz polarization for both the 1D and 2D absorbers are also investigated. The high performance together with the easy fabrication processes presented in this paper show that the plasmonic absorber holds high prospect in terahertz applications.

Stacked pulse-electroplated CoNiMnP–AAO nanocomposite permanent magnets for MEMS

The paper presents a CMOS compatible pulse-electroplating technique combined with a low temperature bonding process for the synthesis of CoNiMnP–AAO (anodic alumina oxide) nanocomposite films and the fabrication of stacked composite permanent magnets (PMs). The magnetic nanocomposite film exhibits the best characteristics of the coercivity of 2472 Oe, remanence of 4000 G, and of 16.13 kJ m−3, in the existing CoNiMnP systems. Meanwhile, a surface magnetic flux density of 9.2 mT generated by a 15-layer-stacked composite PM with a volume of 9 mm3 has shown the potential for various magnetic microelectromechanical systems (MEMS) fabrication using the nanocomposite material.

Bandgap-customizable germanium using lithographically determined biaxial tensile strain for silicon-compatible optoelectronics.

Strain engineering has proven to be vital for germanium-based photonics, in particular light emission. However, applying a large permanent biaxial tensile strain to germanium has been a challenge. We present a simple, CMOS-compatible technique to conveniently induce a large, spatially homogenous strain in circular structures patterned within germanium nanomembranes. Our technique works by concentrating and amplifying a pre-existing small strain into a circular region. Biaxial tensile strains as large as 1.11% are observed by Raman spectroscopy and are further confirmed by photoluminescence measurements, which show enhanced and redshifted light emission from the strained germanium. Our technique allows the amount of biaxial strain to be customized lithographically, allowing the bandgaps of different germanium structures to be independently customized in a single mask process.