Optics and Photonics REsearch Lab OPREL

Nanoscale semiconductor materials and photonic devices are expected to play an important role in addressing ongoing and future challenges in the field of communication and sensing. Ultra high-speed, short and long-range communication links; portable and power-efficient computing devices; ultra-fast interconnects; and high-performance optical sensors in sensing applications are critically depending on the success of next-generation emerging materials and the resulting photonic devices. Therefore, we are fully committed to perform cutting-edge and collaborative experimental research on nanoscale materials and photonic devices. The areas of research focus primarily include advanced materials, novel semiconductor lasers, nanophotonic devices, integrated photonics, nanofabrication, new device concepts and electronic/photonic integration. Group IV, III-V and their alloys as semiconductor materials will mainly be used to design and fabricate these devices.

Schematic at the left illustrating our research work which are dedicated to interdisciplinary research relating to III-V compound semiconductor materials and devices that bridges engineering, optics, applied physics and nanoscience or nanotechnology.

III-Nitride-based Blue lasers

InP-based Photonic Integrated Circuits

 GaN

 The primary research objective of our work is to advance intellectual understanding of non-classical light sources through the development of novel photonic platforms that require growth of one-dimensional III-nitride nanowire (NW) structures. We will explore a new and unique technique for the growth of nitrogen (N)-polar GaN NWs with InGaN quantum dots (QDs) deterministically placed inside using a bottom-up approach via plasma-assisted molecular beam epitaxy (PAMBE). The long-term objective of the proposed research is to achieve bright and ultra-spectrally pure single-photon sources (SPSs) that meet aggressive performance specifications, such as high count rate and near-zero auto-correlation factors for high-fidelity entanglement.

 h-BN

 2D semiconductors have opened up new possibilities due to their potentials as active device materials for future optoelectronics. Among several 2D materials, hexagonal boron nitride (h-BN), a 2D material, is emerging to host ultra bright room-temperature quantum emitters. Our primary research goal is to grow single-crystalline, large-area and defect-free h-BN thin films on highly oriented pyrolitic graphite (HOPG) substrates. Growing high-quality and large-area h-BN thin films through a scalable and controllable method is essential for the demonstration of single-photon emitters (SPEs).

The Nanotech West Lab of Ohio State is the largest nanotechnology user facility in the state of Ohio. Serving both internal (Ohio State) and external users, Nanotech West supports more than 100 research and development projects per year including use many external users, predominantly startup companies in the Ohio region. Nanotech West consists of a 6,000 square foot class 100 cleanroom facility, a 4,000 square foot Biohybrid Laboratory.

Nanotech West is staffed by 7 full-time engineers, 2 part-time support engineers, 1 full-time administrator, and additional Associate Staff and engineering and office student interns. Most of the engineering Core Staff have extensive experience in semiconductor or closely related industries.

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Near Ambient Pressure-X-ray Photoelectron Spectroscopy

The Surface Analysis Lab (SAL) facility within Center of Chemistry and Biochemistry (CBEC) Engineering houses a newly installed SPECS near ambient pressure (NAP) Kratos Axis Ultra XPS system utilizing an in-situ cell capable of surface characterization

in the presence of gases of interest up to 20 mbar and a temperature range of 200-800 K. The instrument is equipped with both monochromatic (Al) and dual (Mg and Al) X-ray sources in addition to a helium UV source. Ar ion gun is also available for sputtering and depth profiling purposes. The smallest spot size that the system is capable of is 50 μm × 50 μm.

The system features the following capabilities:

• Near ambient pressure cell capable of XPS measurements from UHV up to 20 mbar of N2

• 3 Mass flow controllers and a separate leak valve (for vapors) in a premixing line prior to introduction to the cell

• Al anode X-ray source with a variable spot size between 250 µm to 1 mm

• Sample cooling and heating covering the range of 200 K to 825 K

• IQE 12/38 Argon Sputtering source for depth profiling and sputtering

Available Gases:

• O2, CO, CO2, H2, H2O, Alcohol, Ar, N2
• Other gases would be considered upon discussion with the lab manager.

Limitations:

• Sample size should not exceed 1.5 mm × 1.5 mm × 1 mm (L × W × H) in dimensions.

• There is no charge neutralizer available therefore non-conductive samples will significantly charge.

• Powder samples will only be secured via carbon tape. Samples utilizing carbon tape will be limited to room temperature measurements and non-corrosive gases.

XPS vs EDS

• Depth analysis in EDS around 1000 to 2000 nm which is 100 to 200 times deeper than XPS.

• EDS works better for heavier elements.

• XPS analysis works well on insulating materials, as well as on conducting or semiconducting materials.  This avoids conductive coating interference problems that may accompany EDS analysis.

• Because of the charged excitation electron beam, rather than neutral x-rays used in XPS analysis, EDS analysis on some insulating materials is challenging and may be of much reduced usefulness.

• Lithium, beryllium, and boron may be detected and can be quantitatively analyzed with XPS.  The XPS accuracy of analysis for carbon, nitrogen, and oxygen is very high, while it is abysmal for EDS.

Renishaw Raman IR Microprobe 

This instrument is a combination of an inVia confocal Raman microscope for Raman spectroscopy and a Smiths Detection IlluminatIR II for FTIR. The for Raman spectroscopy available are 458, 514, 633 and 785 nm.  With the instrument configuration, it is able to record each spectrum individually or in combination to get a Raman spectra and FTIR on the exact same spot on the sample.  Samples can be film, powder, or liquid.  There is also a temperature cell available to use with films or powder that has a temperature range from -173 to 600 °C. 

• Laser: 514 nm/633 nm/785 nm as pump wavelengths

• Grating: 1800 l/mm

• Exposure time: 10s/20s/30s (User's choice)

• Accumulations: 5/10 (User's choice)

• Laser power: 100%

• Range 100-1600 cm-1

• Objective: 50×

• Beam spot size: 1 mm

Coming soon: Polarized Raman Spectroscopy with the ability to change the polarization of the pump and/or probe for the 514, 633 ad 785 nm Raman pump wavelengths.

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The Center for Electron Microscopy and Analysis (CEMAS) is a centralized, coordinated imaging facility where traditional boundaries between disciplines are eliminated.

With one of the largest concentrations of electron and ion beam analytical microscopy instruments in any North American institution, CEMAS brings together multidisciplinary expertise to drive synergy, amplify characterization capabilities, and challenge what is possible in analytical electron microscopy.

1. Scanning Electron Microscopy (SEM)
2. Transmission Electron Microscopy (TEM)
3. Focused Ion Beam (FIB) Microscopy
4. Cryo-electron Microscopy (CRYO-EM)
5. X-ray Diffraction (XRD)
6. Micro Computed Tomography (MICROCT)

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Backend process

​Indent and Cleaving Solutions

 A LatticeAx 420 includes a monocular microscope with 4 µm optical resolution, color CCD camera cleaves a wide range of materials and sample sizes. It has a highest cleaving accuracy of 10 µm. The Indent position can be controlled with 5 µm step size.

Optical Spectrum Analyzer

 Our Optical Spectrum Analyzer (OSA) "OSA205C" covers the wavelength range from 1 µm to 5.6 µm. The tool acquires the spectrum via Fourier transform, using a scanning Michelson interferometer in a push/pull configuration. This system has two operating modes. One is the spectrometer mode (7.5 GHz Resolution (0.25 cm-1). The other one is wavelength meter mode (0.1 ppm Resolution (Only for <10 GHz Linewidth Sources)). These compact benchtop instruments suit a wide variety of applications, such as analyzing the spectrum of a telecom signal, resolving the Fabry-Perot modes of a gain chip, and identifying gas absorption lines.

Micro-Photoluminescence Spectroscopy

The OPREL Lab’s capabilities in photoluminescence spectroscopy include multiple laser sources with varying excitation wavelengths; a detection range extending from 0.4 to 0.9 µm with a resolution of 0.25 nm and room-temperature measurement. The contactless, nondestructive PL method uses a customized HR4000 spectrometer to analyze the electronic structure of materials. The samples get excited by a collimated laser source at a wavelength above their bandgap. The excited carriers move to the material conduction bands due to the applied photons. Once the excitation ends, the carriers will recombine in the valence band and emit photon energy (Photoluminescence). The characteristic of this emitted photoluminescence is a symbol of the material characteristics and gives information regarding the composition, bandgap, impurity and defect levels, and structure of the materials.

Mini-PL/Raman 

The measurement of photoluminescence (PL) spectra from semiconductor materials is a crucial characterization technique that is commonly used to gather data on bandgap and edge effects, alloy composition, carrier doping levels, and other characteristics. The ability to monitor UV Resonance Raman spectra enhances material characterization and increases specificity. The Deep UV (DUV) MiniPL/Raman Spectrometer from Photon Systems is the most portable and reasonably priced equipment at these wavelengths. This system enables the measurement of semiconductor materials' PL and Raman spectra with bandgaps up to roughly 5.5 eV, or AlGaN with Al concentrations up to about 80%. Equipped with Instec Cryo Stage, the PL/Raman system can operate at both RT and cryo temperature.

Key features: 

• Room / Cryo Temperature PL and Raman
• 248.6nm nm laser excitation
• Highly portable 15 × 18 × 36cm, <8Kg
• High Resolution 0.2nm (multi slits included)
• Detection ranges from 250 nm to 650 nm
• Computer controlled Grating selection and Calibration
• 1200g/mm grating std. (300nm peak)
• Digital PMT controller with gated box car Integrator & Averager for low noise digital PMT output measurement
• Fully integrated, self-contained, system
• LabView interface and control of laser, spectrograph, PMT, spectral data
• X-Y-Z stage manual sample control 50mm standard

Confocal photoluminescence (in progress) 

Currently in the process of building up, the confocal Photoluminescence setup is part of the OPREL lab providing confocal microscopy services for imaging as well as spectroscopy for III-V materials including thin-film and nanowires.

The confocal system is equipped with multiple laser lines (405 nm, 532 nm), a window-corrected objective lens and two state of the art cameras to assist simultaneous imaging and spectroscopy. A high resolution spectrometer with <0.5 nm resolution is attached to the EMCCD camera to make the system ideal to analyze microscopic optical sources i.e. single nanowires, which can generate extreme low level emission.

Key features:  

• Room temperature operation
• Window corrected objective lens (100x, 50x)
• EMCCD Camera for spectroscopy
• CCD camera for imaging
• Multiple lasers for excitation (405 nm, 532 nm)
• x-y-z stage for sample control

PIC Testing  

OPREL has a test setup for measuring vertical fiber-to-chip grating couplers with both 8° and 10° angles of incidence. A tunable laser source (Keysight 81989) spanning the wavelength range from 1465 nm- 1575 nm with a maximum optical output power of 13 dBm is used. An optical power meter (Keysight 81633A) is used for monitoring optical power in the range of 10 dBm - -90 dBm power range. A 3-Axis NanoMax positioner with a 20 nm travel resolution is connected to its sample stage. Butt-coupling can also be done in the setup.

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Lakeshore CRX-6.5k with Keysight B1500A Parameter Analyzer

Photo by NTW Lakeshore CRX Low Temperature Probe Station is connected with Keysight B1500A Parameter Analyzer (PRB07 at NTW). This Probe station enables users to conduct temperature-dependent current-voltage (I-V) and capacitance-voltage (C-V) measurements while accommodating temperature range from 9 K to 300 K.
Optical related measurements such as I-V and C-V under laser illumination can also be undertaken. The in-housing multimode fiber is placed in the probe station, and four different lasers, 660 nm, 890 nm, 1300 nm, and 1550 nm, are available. 
The Easy Expert Software is compatible with the Parameter Analyzer, which helps users customize measurement interface and environment and use it readily.

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