Germanium Window Research Articles

TECHNOLOGY OF VACUUM TIGHT SEALING OF MICROBOLOMETER PACKAGE

The features of the design of micro bolometer packages are considered, the choice of preform material for sealing the package with a soldered seam is made. The characteristics of getter films and the advantages of applying them to the reverse side of a germanium window are presented. A technique for vacuum-tight sealing of micro bolometer packages with germanium windows has been developed.

Thermal Effect of Probes Present in a Pharmaceutical Formulation during Freeze-Drying Measured by Contact-Free Infrared Thermography

A high-resolution infrared (IR) camera was used for temperature measurements in a pharmaceutical formulation (mannitol/sucrose solution, 4:1%, m/m) during a freeze-drying process. The temperature was measured simultaneously at the surface as well as vertically (e.g., in-depth) along the side of custom-made cuvettes equipped with a germanium (Ge) window. Direct imaging during 45 h from −40 °C to 40 °C took place every 60 s on the surface and on the side with 0.28 × 0.28 mm per IR-pixel providing 2700 thermograms. The spatial resolution per cuvette was approximately 4225 pixels for the surface view (without a probe) and 6825 IR-pixels for the side view. Temperature effects and gradients due to the presence of a Pt100 and a LyoRx-probe in the pharmaceutical formulation were clearly visible and were quantified during the freezing step as well as the primary and secondary drying stages. The temperature was about 3.5 K higher during primary drying as compared to the temperature measured in the same material in adjacent cuvettes without probes. During secondary drying, evaporative cooling of upper layers was clearly visible.

Infrared Thermography for Monitoring of Freeze Drying Processes-Part 2: Monitoring of Temperature on the Surface and Vertically in Cuvettes during Freeze Drying of a Pharmaceutical Formulation.

The coupling of an infrared (IR) camera to a freeze dryer for monitoring of the temperature of a pharmaceutical formulation (sucrose/mannitol solution, 4:1%, m/m) during freeze-drying has been exploited further. The new development allows monitoring of temperatures simultaneously at the surface as well as vertically, (e.g., in depth) along the side using custom-made cuvettes. The IR camera was placed on the chamber roof of a process-scale freeze dryer. Monitoring of cuvettes containing the formulation took place from above where one side of each cuvette was equipped with a germanium window. The Ge-window was placed next to an IR mirror having a 45° angle. The long-wave infrared radiation (LWIR) coming from the inside of the cuvette was reflected upwards toward the IR camera. Accurate recording of the temperature along the cuvettes’ depth profile was therefore possible. Direct imaging from −40 °C to 30 °C took place every 60 s on the surface and on the side with a 2 × 2 mm resolution per IR pixel for 45 h resulting in 2700 thermograms. Results are presented for freeze-drying of a pharmaceutical formulation as a function of time and spatially for the entire side (depth) of the cuvette. As the sublimation process was progressing, the spatial resolution (84 IR pixels for the side-view and 64 pixels for the surface-view) was more than sufficient to reveal lower temperatures deeper down in the material. The results show that the pharmaceutical formulation (a true solution at the onset) dries irregularly and that the sublimation front does not progress evenly through the material. During secondary drying, potential evaporative cooling of upper layers could be detected thanks to the high thermal and spatial resolution.

Synthesis of high hardness IR optical coating using diamond-like carbon by PECVD at room temperature

Diamond-like Carbon (DLC) for IR antireflective properties is currently being used in the coating of germanium based IR optics. These DLC coatings offer better wear resistance as compared to traditional anti-reflective (AR) coatings. The current work emphasizes the development of IR optics using germanium substrate coated with DLC which typically covers IR transmission in wavelength regions like 3–7μm and 9–15μm. In order to study IR transmission, an optimum film thickness of DLC was calculated and coated on a double sided polished germanium substrate. DLC was coated on a single side of a germanium substrate, as well as on both sides of germanium. DLC has been deposited using Radio Frequency Plasma Enhanced Chemical Vapour Deposition (RF-PECVD) at room temperature without the use of any intermediary buffer layers required for adhesion and high hardness values were achieved at room temperature as compared to existing literature. The transmission of IR through DLC coated germanium windows was measured using Fourier Transform Infra-Red (FTIR) spectroscopy. A comparison between transmission through a single side and double sided DLC coating on germanium has been demonstrated. The hardness of the film was measured using nanoindentation. Scratch test was also performed using nanoindentation. Adhesion and salt spray tests were performed as per MIL standards. With double sided DLC coating, a peak transmission value of 93% is achieved in 3–7μm and the average hardness of DLC is measured to be 32.74GPa.

New experimental results on local heat transfer inside a rectangular channel with rib-roughened surfaces

In this paper we present new experimental results on local heat transfer characteristics of a forced air-flow through a 12-mm-height, rectangular channel of 1:10 aspect ratio, with square-cross-section ribs mounted onto the lower surface. Data are collected on a completely redesigned test section. Specifically, the electric heater is made of very thin copper tracks, in direct contact with the air flow and covering at 97.5% the channel lower surface to guarantee a very uniform heat flux. The copper tracks are laminated onto a 2-mm thick board of FR-4 glass epoxy to provide negligible heat conduction inside the plate and heat losses from its sides. Finally, the channel walls are in XPS and, into the upper one, a double glazing consisting of two 120 mm x 120 mm Germanium windows is mounted to allow optical access to the IR camera and to reduce local heat dispersions. Data here presented refer to convection over 4 mm x 2 mm ribs in transverse configuration for Reynolds numbers, based on the duct hydraulic diameter, ranging between 700 and 8000. Preliminary tests show how the new apparatus has significantly improved the quality, the ease and the quickness of the measurements.

Nickel and Gold Coatings of Germanium and Kovar Substrates

The integration of germanium to other materials such as Kovar® (registered trademark of Carpenter Technology Corporation), an Fe-Ni-Co alloy, by soldering requires a surface preparation due to poor wetting characteristics of germanium. Coating (metallization) by successive electroplating of 3 mm wide nickel and gold frames well adhered to the outer edge of a circular germanium window and kovar body was applied to attain successful joining of germanium to kovar. Surface cleaning of parts to be joined or plated plays an important role in the quality of the depositions. HF and HCl solutions were used for germanium surface cleaning and the results showed that HF solution was more effective than HCl in terms of removing oxide capability. The desired small grain sized solderable nickel layer was achieved by pulse plating from Watts solution. Likewise, non-porous very thin gold was deposited by pulse plating again and it prevented the diffusion of oxygen to nickel and diffusion of nickel to the free surface. Characterization of the coatings were performed in terms of microstructure, roughness and elemental analysis by scanning electron microscopy (SEM), white light interferometry and x-ray photoelectron spectroscopy (XPS), respectively.

Nickel and Gold Coatings of Germanium and Kovar Substrates

The integration of germanium to other materials such as Kovar®(registered trademark of Carpenter Technology Corporation), an Fe-Ni-Co alloy, by soldering requires a surface preparation due to poor wetting characteristics of germanium. Coating (metallization) by successive electroplating of 3 mm wide nickel and gold frames well adhered to the outer edge of a circular germanium window and kovar body was applied to attain successful joining of germanium to kovar. Surface cleaning of parts to be joined or plated plays an important role in the quality of the depositions. HF and HCl solutions were used for germanium surface cleaning and the results showed that HF solution was more effective than HCl in terms of removing oxide capability. The desired small grain sized solderable nickel layer was achieved by pulse plating from Watts solution. Likewise, non-porous very thin gold was deposited by pulse plating again and it prevented the diffusion of oxygen to nickel and diffusion of nickel to the free surface. Characterization of the coatings were performed in terms of microstructure, roughness and elemental analysis by scanning electron microscopy (SEM), white light interferometry and x-ray photoelectron spectroscopy (XPS), respectively.

Infrared thermography measurement of two-phase boiling flow heat transfer in a microchannel

In this study, a non-intrusive method to directly measure the fluid temperature and two-phase flow patterns in micro-scale system was developed. To achieve this goal, an adequate calibration process of infrared (IR) thermography measurement and an experimental design of IR transparent convective flow in a microchannel were established. The temperature distribution of the fluid along the microchannel was measured by IR thermography through a germanium window of thickness 5 mm. The transparent germanium window was used to facilitate the transmission of long-wavelength IR rays. The infrared images were obtained at a frame rate of 200 fps, which enabled observation of the transient temperature behavior during flow boiling in the microchannel. A semi-transparent liquid, namely ethanol, was used as the working fluid, with a mass flux of 20.3 kg/m2s and heat flux range of 3.1–244.1 kW/m2. The experimental results confirmed that IR thermography could be used to capture the transient single- and two-phase flow patterns as well as the fluid temperature along the channel. To the best of our knowledge, this paper is the first presentation of IR visualization of two-phase flow patterns in a microchannel. The trends of the local heat transfer coefficients with respect to the two-phase flow patterns are discussed, and the experimentally determined coefficients are compared with those calculated by commonly used equations.

저가형 열영상 시스템을 위한 실리콘 윈도우 제작

An infrared (IR) bolometer measures the change of resistance by absorbing incident IR radiation and generates a signal as a function of the radiation intensity. Since a bolometer requires temperature stabilization and light filtering except for the infrared rays, it is essential for the device to be packaged meeting conditions that above mentioned. Minimization of heat loss is needed in order to stabilize temperature of bolometer. Heat loss by conduction or convection requires a medium, so the heat loss will be minimized if the medium is a vacuum. Therefore, vacuum packaging for bolometer is necessary. Another important element in bolometer packaging is germanium (Ge) window, which transmits IR radiation to heat the bolometer. To ensure a complete transmittance of IR light, anti-reflection (AR) coatings are deposited on both sides of the window. Although the transmittance of Ge window is high for IR rays, it is difficult to use frequently in low-price IR bolometer because of its high price. In this paper, we fabricated IR window by utilizing silicon (Si) substrate instead of Ge in order to reduce the cost of bolometer packaging. To enhance the IR transmittance through Si substrate, it is textured using Reactive Ion Etching (RIE). The texturing process of Si substrate is performed along with the change of experimental conditions such as gas ratio, pressure, etching time and RF power.

Preparation of Surfaces of Germanium and Kovar Substrates By Electroplating for Soldering

Germanium is used as a window material in packaging infrared detector structures, due to its high refractive index and transmittance to infrared radiation. It must be joined to the dewar body made of Kovar® (registered trademark of Carpenter Technology Corporation) material by soldering during packaging. A surface coating (metallization) well adhered to both substrates was developed as a surface preparation step prior to soldering to overcome the poor wetting characteristics of germanium. Successive electroplating of 3 mm wide nickel and gold frames to the outer edge of a circular germanium window and kovar body was applied to attain successful joining of germanium to kovar. Surface cleaning of parts to be joined or plated is very essential to remove contaminants from the surface and reduce oxides to the highest possible extent. Onsia and Conard [1], reported that wet chemical processes need to be developed to prepare germanium surface for subsequent growth processes. The wet chemical treatment for germanium surface preparation used in this study followed the reciepe originally proposed by Shiyu Sun et. Al. [2]. The samples were first dipped into deionized water having a resistivity of 18.6 MΩ cm, for 30 seconds to dissolve the native oxide. Then, they were placed into 10% H2O2 solution for 30 seconds to eliminate the carbon contaminations on the surface. Finally, the samples were immersed into a hydrofluoric acid solution for 10 minutes to remove the oxides. X-Ray Photoelectron Spectroscopy (XPS) results showed that more than 70% of oxides on the surface could be eliminated by the surface preparation treatment proposed above. A chemical polishing method was applied for kovar surface cleaning. Solution bath was composed of 750 mL CH3COOH (Sigma Aldrich, 1005706), 250 mL HNO3 (Sigma Aldrich, 438073) and 3 mL HCl (Sigma Aldrich, 438073). The temperature was kept constant at 60°C and the solution was not stirred during cleaning. The nickel was deposited at 55oC from the Watts solution, containing 240 g/L NiSO4.6H2O, 45 g/L NiCl2.6H2O and 30 g/L boric acid (Merck, 100165), because it is easy to control the bath and deposits have lower internal stresses. The wave characteristic of pulse current and saccharin addition have important effects in nickel plating [3] in terms of porosity, grain size and densty of coatings Addition of saccharin to the bath and the use of pulse plating decreased the grain size of the nickel and changed the morphology of the grains from pyramidal structure to colony like in coating. A thin layer of gold, as pore free as possible, was required to protect the nickel surface from oxidation. Gold was electrodeposited on the nickel coated kovar substrate from the acid cyanide bath at 50oC by pulse and direct current plating in this study. The bath was composed of 10 g/L potassium gold cyanide and 180 g/L potassium citrate. The gold films obtained by pulse plating exhibited stronger adhesion to nickel surface and contained less porosity compared to DC plating. The porosity of gold coating was determined by the IPC-TM-650 test method. The solution used in porosity test was composed of 980 mL ethanol, 7 g dimethylglyoxim (Sigma Aldrich, 162574), 20 mL de-ionized water and 1 g ammonium chloride (Merck, 168320). The increase in gold deposit thickness in 0.1 to 0.4 µm range decreased porosity.

A hybrid antireflection coating with a diamondlike layer

This paper discusses questions of the development of a protective antireflection coating with a diamondlike layer for germanium windows of thermal-vision devices. The hybrid coating thus developed has enhanced transmission in the 8–12-μm region by comparison with an ordinary diamondlike coating.

Infrared Thermography for Monitoring of Freeze-Drying Processes: Instrumental Developments and Preliminary Results

Coupling an infrared (IR) camera to a freeze dryer for on-line monitoring of freeze-drying cycles is described for the first time. Normally, product temperature is measured using a few invasive Pt-100 probes, resulting in poor spatial resolution. To overcome this, an IR camera was placed on a process-scale freeze dryer. Imaging took place every 120 s through a Germanium window comprising 30,000 measurement points obtained contact-free from −40°C to 25°C. Results are presented for an empty system, bulk drying of cheese slurry, and drying of 1 mL human serum in 150 vials. During freezing of the empty system, differences of more than 5°C were measured on the shelf. Adding a tray to the empty system, a difference of more than 8°C was observed. These temperature differences probably cause different ice structures affecting the drying speed during sublimation. A temperature difference of maximum 13°C was observed in bulk mode during sublimation. When drying in vials, differences of more than 10°C were observed. Gradually, the large temperature differences disappeared during secondary drying and products were transformed into uniformly dry cakes. The experimental data show that the IR camera is a highly versatile on-line monitoring tool for different kinds of freeze-drying processes. © 2014 European Union 103:2088–2097, 2014

Design and Analysis of Hermetic Single Chip Packaging for Large Format Thermistor

The paper presents the hermetic thermistor sensor packaging with 12.8mm×9.6mm used in exothermic reactions detection. The mechanical analysis was conducted including the germanium (Ge) window stress and deformation caused by process stress and vacuum effects. The maximum deformation of Ge window is about 281.5μm and the stress intensity is about 650.19MPa. YbF3 with the thickness of 1.36μm and 1.09μm are used as double-layer antireflection films to weaken the reflection incidents. The transmission is 87.82% for 8-14μm wavelengths as calculated. The paper also presents the influence of vacuum environment on detectors performance. The results suggest that the temperature response approaching to theoretical value when the chamber pressure is lower than 0.01 mbar. At last, this work illustrates the process flow and fabrication details of the packaging devices.

Determination of the mid-IR femtosecond surface-damage threshold of germanium

To assess the potential uses of germanium as a nonlinear material in the mid IR we have measured the surface-damage threshold of germanium optical windows using femtosecond pulses at a wavelength of 3.9 μm. By working with a wavelength corresponding to a photon energy of less than half the band-gap energy, free-carrier generation due to one- and two-photon absorption was eliminated. The laser pulses had an energy of 5.5 μJ, a duration of 255 fs, and were focused to a waist size of approximately 100 μm. The multi-shot damage threshold of the germanium windows was estimated to be approximately 94 GW/cm2. The data should be of immediate benefit to industrial laser researchers and applications engineers working in the mid-IR region.

높은 열저항 계수를 가지는 비냉각형 적외선 열영상 이미지 센서용 MDTF(Metal-dielectric Thin Film)에 관한 연구

In this paper, fabricated by MEMS uncooled micro-bolometer detector for the study in the infrared sensitivity enhancement. Absorption layer SiOx-Metal series MDTF (metal-dielectric thin film) by high absorption rate and has a high thermal coefficient of resistance, low noise characteristics were implemented. Then MDTF were made in a vacuum deposition method. And MDTF for the analysis of the physical properties of silicon wafers were fabricated, TCR (temperature coefficient of resistance) value was made in order to measure the glass wafer and FT-IR (Fourier Transform Infrared spectroscopy) values were made in order to measure the germanium window. The analyzed results of MDTF -3 [%/K] has more characteristics of the TCR. And 8~12 um wavelength region close to 70% in the absorption characteristic.

The Best Control of Parasitic BJT Effect in SOI-LDMOS With SiGe Window Under Channel

The floating-body effect and impact ionization generate excess holes that are amplified by the parasitic bipolar junction transistor (BJT) in silicon-on-insulator lateral double-diffused MOSFETs (SOI-LDMOS) that degrade the transistor performance. In this paper, a novel silicon germanium (SiGe) window LDMOS on SOI (SW-SOI) is reported where the buried oxide under the channel region becomes thinner and a SiGe window has been replaced in order to reduce the hole concentration in the channel and control the BJT effect significantly. The novel features of an SW-SOI are simulated and compared with a conventional LDMOS on SOI (C-SOI). In addition, reduced self-heating effects and higher breakdown voltage have been achieved as compared with the C-SOI. Hence, this paper illustrates the benefits of the high performance SW-SOI device over a conventional one and expands the application of SOI MOSFETs to high temperature.

锗窗口红外宽光谱增透膜的研制

锗窗口红外宽光谱增透膜的研制

锗窗口红外宽光谱增透膜的研制

锗窗口红外宽光谱增透膜的研制

PROPERTIES OF OPTICAL WINDOWS FOR IR SENSORS

Properties of IR sensor windows which are used for the photodetectors working in conditions of hard radiation are investigated. Germanium, gallium arsenide and indium antimonide crystals windows property change is investigated. It is shown, that such changes depend on initial properties and occurrence of structural defects.

Time-resolved reflectance and transmittance measurements of laser-induced free carriers in germanium, silicon, and zinc selenide at 106 μm

We present experimental results of reflectance and transmittance measurements of infrared radiation by high-density photogenerated free carriers in polycrystalline germanium, polycrystalline silicon, and chemical vapor deposition zinc selenide windows. Linearly polarized 1064 and 532 nm wavelength light from a Nd:YAG laser with a 130 ps pulse width were used to generate free carriers in the samples. Reflectance and transmittance were measured at a 10.6 microm wavelength using a linearly polarized CO2 laser.