Enhanced LWIR response of InP/InAsP quantum discs-in-nanowire array photodetectors by photogating and ultra-thin ITO contacts.

Here we report on an experimental and theoretical investigation of the long-wavelength infrared (LWIR) photoresponse of photodetectors based on arrays of three million InP nanowires with axially embedded InAsP quantum discs. An ultra-thin top indium tin oxide contact combined with a novel photogating mechanism facilitates an improved LWIR normal incidence sensitivity in contrast to traditional planar quantum well photodetectors. The electronic structure of the quantum discs, including strain and defect-induced photogating effects, and optical transition matrix elements were calculated by an 8-bandk·psimulation along with solving drift-diffusion equations to unravel the physics behind the generation of narrow linewidth intersubband signals observed from the quantum discs.

Nanopatterned rGO/ZnO:Al seed layer for vertical growth of single ZnO nanorods.

In this work, we demonstrate a novel low-cost template-assisted route to synthesize vertical ZnO nanorod arrays on Si (100). The nanorods were grown on a patterned double seed layer comprised of reduced graphene oxide (rGO) and Al-doped ZnO nanoparticles. The seed layer was fabricated by spray-coating the substrate with graphene and then dip-coating it into a Al-doped ZnO sol-gel solution. The growth template was fabricated from a double-layer resist, spin-coated on top of the rGO/ZnO:Al seed layer, and patterned by colloidal lithography. The results show a successful chemical bath deposition of vertically aligned ZnO nanorods with controllable diameter and density in the nanoholes in the patterned resist mask. Our novel method can presumably be used to fabricate electronic devices on virtually any smooth substrate with a thermal budget of 1 min at 300 °C with the seed layer acting as a conductive strain-relieving back contact. The top contact can simply be made by depositing a suitable transparent conductive oxide or metal, depending on the specific application.

Plutonium Signatures in a Dated Sediment Core as a Tool to Reveal Nuclear Sources in the Baltic Sea.

Plutonium distribution was studied in an undisturbed sediment core sampled from the Tvären bay in the vicinity of the Studsvik nuclear facility in Sweden. The complete analysis, including minor isotopes, of the Pu isotope composition (238Pu, 239Pu, 240Pu, 241Pu, 242Pu, and 244Pu) allowed us to establish the Pu origin in this area of the Baltic Sea and to reconstruct the Studsvik aquatic release history. The results show highly enriched 239Pu, probably originating from the Swedish nuclear program in the 1960s and 1970s and the handling of high burn-up nuclear fuel in the later years. In addition, the 244Pu/239Pu atomic ratio for the global fallout period between 1958 and 1965 is suggested to be (7.94 ± 0.31)·10-5. In the bottom layer of the sediment, dated 1953-1957, we detected a higher average 244Pu/239Pu ratio of (1.51 ± 0.11)·10-4, indicating the possible impact of the first US thermonuclear tests (1952-1958).

Electrical transport properties of InAs nanowires synthesized by a solvothermal method.

Nanowires are widely considered to be key elements in future disruptive electronics and photonics. This paper presents the first detailed study of transport mechanisms in single-crystalline InAs nanowires synthesized by a cheap solvothermal wet chemical method. From detailed analyses of temperature-dependent current-voltage characteristics, it was observed that contacted nanowires operate in a linear transport regime at biases below a critical cross-over voltage. For larger biases, the transport changes to space-charge-limited conduction assisted by traps. The characteristic parameters such as free electron concentration, trap concentration and energy distribution, and electron mobility were all calculated. It was demonstrated that the nanowires have key electrical properties comparable to those of InAs nanowires grown by molecular beam epitaxy. Our results might pave the way for cheap disruptive low-dimensional electronics such as resistive switching devices.

Embedded sacrificial AlAs segments in GaAs nanowires for substrate reuse.

We report on the use of a sacrificial AlAs segment to enable substrate reuse for nanowire synthesis. A silicon nitride template was deposited on a p-type GaAs substrate. Then a pattern was transferred to the substrate by nanoimprint lithography and reactive ion etching. Thermal evaporation was used to define Au seed particles. Metalorganic vapour phase epitaxy was used to grow AlAs-GaAs NWs in the vapour-liquid-solid growth mode. The yield of synthesised nanowires, compared to the number expected from the patterned template, was more than 80%. After growth, the nanowires were embedded in a polymer and mechanically removed from the parent substrate. The parent substrate was then immersed in an HCl:H2O (1:1) mixture to dissolve the remaining stub of the sacrificial AlAs segment. The pattern fidelity was preserved after peeling off the nanowires and cleaning, and the semiconductor surface was flat and ready for reuse. Au seed particles were then deposited on the substrate by use of pulse electrodeposition, which was selective to the openings in the growth template, and then nanowires were regrown. The yield of regrowth was less optimal compared to the first growth but the pattern was preserved. Our results show a promising approach to reduce the final cost of III-V nanowire based solar cells.

Evaluation of carrier density and mobility in Mn ion-implanted GaAs:Zn nanowires by Raman spectroscopy.

The fabrication of complex nanoscale electronics with reduced dimensions poses challenges on novel techniques to accurately determine fundamental electronic parameters. In this article, we present a universal contactless method based on Raman scattering for measuring the mobility and hole concentration independently in GaAs:Zn and Mn ion-implanted GaAs:Zn nanowires, potentially of great interest for spintronics applications. Clear coupled longitudinal optical phonon-plasmon modes were recorded and fitted with a dielectric function, based on the Drude model, which includes contributions from both plasmons and phonons. From the fitting, we extract accurate values of the plasma frequency and plasma damping constant from which we directly calculate the hole density and mobility, respectively. The extracted mobilities were also used as input data for analysis of complementary four-probe transport measurements, where the corresponding hole concentrations could be calculated and found to be in good agreement with those extracted directly from the Raman data. We also investigated the influence of annealing of the GaAs:Zn nanowires on the hole concentration and mobility and found strong indications of thermally activated defects related to a formed crystalline As/oxide shell around the nanowires. The method proposed here is extremely powerful for the characterization of nanoelectronics in general, and nanospintronics in particular for which Hall measurements are difficult to pursue due to problems related to contact formation, as well as to inherent magnetic properties of the devices.

High Responsivity of InP/InAsP Nanowire Array Broadband Photodetectors Enhanced by Optical Gating.

High-performance photodetectors operating in the near-infrared (0.75-1.4 µm) and short-wave infrared (1.4-3.0 µm) portion of the electromagnetic spectrum are key components in many optical systems. Here, we report on a combined experimental and theoretical study of square millimeter array infrared photodetectors comprising 3 million n+-i-n+ InP nanowires grown by MOVPE from periodically ordered Au seed particles. The nominal i-segment, comprising 20 InAs0.40P0.60 quantum discs, was grown by use of an optimized Zn doping to compensate the nonintentional n-doping. The photodetectors exhibit bias- and power-dependent responsivities reaching record-high values of 250 A/W at 980 nm/20 nW and 990 A/W at 532 nm/60 nW, both at 3.5 V bias. Moreover, due to the embedded quantum discs, the photoresponse covers a broad spectral range from about 0.70 to 2.5 eV, in effect outperforming conventional single InGaAs detectors and dual Si/Ge detectors. The high responsivity, and related gain, results from a novel proposed photogating mechanism, induced by the complex charge carrier dynamics involving optical excitation and recombination in the quantum discs and interface traps, which reduces the electron transport barrier between the highly doped n+ contact and the i-segment. The experimental results obtained are in perfect agreement with the proposed theoretical model and represent a significant step forward toward understanding gain in nanoscale photodetectors and realization of commercially viable broadband photon detectors with ultrahigh gain.

Raman characterization of single-crystalline Ga0.96Mn0.04As:Zn nanowires realized by ion-implantation.

Recent progress in the realization of magnetic GaAs nanowires (NWs) doped with Mn has attracted a lot of attention due to their potential application in spintronics. In this work, we present a detailed Raman investigation of the structural properties of Zn doped GaAs (GaAs:Zn) and Mn-implanted GaAs:Zn (Ga0.96Mn0.04As:Zn) NWs. A significant broadening and redshift of the optical TO and LO phonon modes are observed for these NWs compared to as-grown undoped wires, which is attributed to strain induced by the Zn/Mn doping and to the presence of implantation-related defects. Moreover, the LO phonon modes are strongly damped, which is interpreted in terms of a strong LO phonon-plasmon coupling, induced by the free hole concentration. Moreover, we report on two new interesting Raman phonon modes (191 and 252 cm-1) observed in Mn ion-implanted NWs, which we attribute to Eg (TO) and A1g (LO) vibrational modes in a sheet layer of crystalline arsenic present on the surface of the NWs. This conclusion is supported by fitting the observed Raman shifts for the SO phonon modes to a theoretical dispersion function for a GaAs NW capped with a dielectric shell.

Intersubband Quantum Disc-in-Nanowire Photodetectors with Normal-Incidence Response in the Long-Wavelength Infrared.

Semiconductor nanowires have great potential for realizing broadband photodetectors monolithically integrated with silicon. However, the spectral range of such detectors has so far been limited to selected regions in the ultraviolet, visible, and near-infrared regions. Here, we report on the first intersubband nanowire heterostructure array photodetectors exhibiting a spectrally resolved photoresponse from the visible to long-wavelength infrared. In particular, the infrared response from 3 to 20 µm is enabled by intersubband transitions in low-bandgap InAsP quantum discs synthesized axially within InP nanowires. The intriguing optical characteristics, including unexpected sensitivity to normal incident radiation, are explained by excitation of the longitudinal component of optical modes in the photonic crystal formed by the nanostructured portion of the detectors. Our results provide a generalizable insight into how broadband nanowire photodetectors may be designed and how engineered nanowire heterostructures open up new, fascinating opportunities for optoelectronics.

Influence of morphology on electrical and optical properties of graphene/Al-doped ZnO-nanorod composites.

The development of future 3D-printed electronics relies on the access to highly conductive inexpensive materials that are printable at low temperatures (<100 ◦C). The implementation of available materials for these applications are, however, still limited by issues related to cost and printing quality. Here, we report on the simple hydrothermal growth of novel nanocomposites that are well suited for conductive printing applications. The nanocomposites comprise highly Al-doped ZnO nanorods grown on graphene nanoplatelets (GNPs). The ZnO nanorods play the two major roles of (i) preventing GNPs from agglomerating and (ii) promoting electrical conduction paths between the graphene platelets. The effect of two different ZnO-nanorod morphologies with varying Al-doping concentration on the nanocomposite conductivity and the graphene dispersity are investigated. Time-dependent absorption, photoluminescence and photoconductivity measurements show that growth in high pH solutions promotes a better graphene dispersity, higher doping levels and enhanced bonding between the graphene and the ZnO nanorods. Growth in low pH solutions yields samples characterized by a higher conductivity and a reduced number of surface defects. These samples also exhibit a large persistent photoconductivity attributed to an effective charge separation and transfer from the nanorods to the graphene platelets. Our findings can be used to tailor the conductivity of novel printable composites, or for fabrication of large volumes of inexpensive porous conjugated graphene-semiconductor composites.

Optimization of Current Injection in AlGaInP Core-Shell Nanowire Light-Emitting Diodes.

Core-shell nanowires offer great potential to enhance the efficiency of light-emitting diodes (LEDs) and expand the attainable wavelength range of LEDs over the whole visible spectrum. Additionally, nanowire (NW) LEDs can offer both improved light extraction and emission enhancement if the diameter of the wires is not larger than half the emission wavelength (λ/2). However, AlGaInP nanowire LEDs have so far failed to match the high efficiencies of traditional planar technologies, and the parameters limiting the efficiency remain unidentified. In this work, we show by experimental and theoretical studies that the small nanowire dimensions required for efficient light extraction and emission enhancement facilitate significant loss currents, which result in a low efficiency in radial NW LEDs in particular. To this end, we fabricate AlGaInP core-shell nanowire LEDs where the nanowire diameter is roughly equal to λ/2, and we find that both a large loss current and a large contact resistance are present in the samples. To investigate the significant loss current observed in the experiments in more detail, we carry out device simulations accounting for the full 3D nanowire geometry. According to the simulations, the low efficiency of radial AlGaInP nanowire LEDs can be explained by a substantial hole leakage to the outer barrier layer due to the small layer thicknesses and the close proximity of the shell contact. Using further simulations, we propose modifications to the epitaxial structure to eliminate such leakage currents and to increase the efficiency to near unity without sacrificing the λ/2 upper limit of the nanowire diameter. To gain a better insight of the device physics, we introduce an optical output measurement technique to estimate an ideality factor that is only dependent on the quasi-Fermi level separation in the LED. The results show ideality factors in the range of 1-2 around the maximum LED efficiency even in the presence of a very large voltage loss, indicating that the technique is especially attractive for measuring nanowire LEDs at an early stage of development before electrical contacts have been optimized. The presented results and characterization techniques form a basis of how to simultaneously optimize the electrical and optical efficiency of core-shell nanowire LEDs, paving the way to nanowire light emitters that make true use of larger-than-unity Purcell factors and the consequently enhanced spontaneous emission.

Room-temperature InP/InAsP Quantum Discs-in-Nanowire Infrared Photodetectors.

The possibility to engineer nanowire heterostructures with large bandgap variations is particularly interesting for technologically important broadband photodetector applications. Here we report on a combined study of design, fabrication, and optoelectronic properties of infrared photodetectors comprising four million n+-i-n+ InP nanowires periodically ordered in arrays. The nanowires were grown by metal-organic vapor phase epitaxy on InP substrates, with either a single or 20 InAsP quantum discs embedded in the i-segment. By Zn compensation of the residual n-dopants in the i-segment, the room-temperature dark current is strongly suppressed to a level of pA/NW at 1 V bias. The low dark current is manifested in the spectrally resolved photocurrent measurements, which reveal strong photocurrent contributions from the InAsP quantum discs at room temperature with a threshold wavelength of about 2.0 µm and a bias-tunable responsivity reaching 7 A/W@1.38 µm at 2 V bias. Two different processing schemes were implemented to study the effects of radial self-gating in the nanowires induced by the nanowire/SiOx/ITO wrap-gate geometry. Summarized, our results show that properly designed axial InP/InAsP nanowire heterostructures are promising candidates for broadband photodetectors.

Defect-induced infrared electroluminescence from radial GaInP/AlGaInP quantum well nanowire array light- emitting diodes.

Radial GaInP/AlGaInP nanowire array light-emitting diodes (LEDs) are promising candidates for novel high-efficiency solid state lighting due to their potentially large strain-free active emission volumes compared to planar LEDs. Moreover, by proper tuning of the diameter of the nanowires, the fraction of emitted light extracted can be significantly enhanced compared to that of planar LEDs. Reports so far on radial growth of nanowire LED structures, however, still point to significant challenges related to obtaining defect-free radial heterostructures. In this work, we present evidence of optically active growth-induced defects in a fairly broad energy range in vertically processed radial GaInP/AlGaInP quantum well nanowire array LEDs using a variety of complementary experimental techniques. In particular, we demonstrate strong infrared electroluminescence in a spectral range centred around 1 eV (1.2 µm) in addition to the expected red light emission from the quantum well. Spatially resolved cathodoluminescence studies reveal a patchy red light emission with clear spectral features along the NWs, most likely induced by variations in QW thickness, composition and barriers. Dark areas are attributed to infrared emission generated by competing defect-assisted radiative transitions, or to trapping mechanisms involving non-radiative recombination processes. Possible origins of the defects are discussed.

Bias-dependent spectral tuning in InP nanowire-based photodetectors.

Nanowire array ensembles contacted in a vertical geometry are extensively studied and considered strong candidates for next generations of industrial scale optoelectronics. Key challenges in this development deal with optimization of the doping profile of the nanowires and the interface between nanowires and transparent top contact. Here we report on photodetection characteristics associated with doping profile variations in InP nanowire array photodetectors. Bias-dependent tuning of the spectral shape of the responsivity is observed which is attributed to a Schottky-like contact at the nanowire-ITO interface. Angular dependent responsivity measurements, compared with simulated absorption spectra, support this conclusion. Furthermore, electrical simulations unravel the role of possible self-gating effects in the nanowires induced by the ITO/SiO x wrap-gate geometry. Finally, we discuss possible reasons for the observed low saturation current at large forward biases.

A comparative study of absorption in vertically and laterally oriented InP core-shell nanowire photovoltaic devices.

We have compared the absorption in InP core-shell nanowire p-i-n junctions in lateral and vertical orientation. Arrays of vertical core-shell nanowires with 400 nm pitch and 280 nm diameter, as well as corresponding lateral single core-shell nanowires, were configured as photovoltaic devices. The photovoltaic characteristics of the samples, measured under 1 sun illumination, showed a higher absorption in lateral single nanowires compared to that in individual vertical nanowires, arranged in arrays with 400 nm pitch. Electromagnetic modeling of the structures confirmed the experimental observations and showed that the absorption in a vertical nanowire in an array depends strongly on the array pitch. The modeling demonstrated that, depending on the array pitch, absorption in a vertical nanowire can be lower or higher than that in a lateral nanowire with equal absorption predicted at a pitch of 510 nm for our nanowire geometry. The technology described in this Letter facilitates quantitative comparison of absorption in laterally and vertically oriented core-shell nanowire p-i-n junctions and can aid in the design, optimization, and performance evaluation of nanowire-based core-shell photovoltaic devices.

III-V nanowire synthesis by use of electrodeposited gold particles.

Semiconductor nanowires are great candidates for building novel electronic devices. Considering the cost of fabricating such devices, substrate reuse and gold consumption are the main concerns. Here we report on implementation of high throughput gold electrodeposition for selective deposition of metal seed particles in arrays defined by lithography for nanowire synthesis. By use of this method, a reduction in gold consumption by a factor of at least 300 was achieved, as compared to conventional thermal evaporation for the same pattern. Because this method also facilitates substrate reuse, a significantly reduced cost of the final device is expected. We investigate the morphology, crystallography, and optical properties of InP and GaAs nanowires grown from electrodeposited gold seed particles and compare them with the properties of nanowires grown from seed particles defined by thermal evaporation of gold. We find that nanowire synthesis, as well as the material properties of the grown nanowires are comparable and quite independent of the gold deposition technique. On the basis of these results, electrodeposition is proposed as a key technology for large-scale fabrication of nanowire-based devices.

Magnetic polarons and large negative magnetoresistance in GaAs nanowires implanted with Mn ions.

We report on low-temperature magnetotransport and SQUID measurements on heavily doped Mn-implanted GaAs nanowires. SQUID data recorded at low magnetic fields exhibit clear signs of the onset of a spin-glass phase with a transition temperature of about 16 K. Magnetotransport experiments reveal a corresponding peak in resistance at 16 K and a large negative magnetoresistance, reaching 40% at 1.6 K and 8 T. The negative magnetoresistance decreases at elevated temperatures and vanishes at about 100 K. We interpret our transport data in terms of spin-dependent hopping in a complex magnetic nanowire landscape of magnetic polarons, separated by intermediate regions of Mn impurity spins, forming a paramagnetic/spin-glass phase.

Uranium Body Clearance Kinetics-A Long-term Follow-up Study of Retired Nuclear Fuel Workers.

ABSTRACT: Nuclear industry workers exposed to uranium aerosols may risk kidney damage and radiation-induced cancer. This warrants the need for well-established dose and risk assessments, which can be greatly improved by using material-specific absorption parameters in the ICRP Human Respiratory Tract Model. The present study focuses on the evaluation of the slow dissolution rate ( s s , d -1 ), a parameter that is difficult to quantify with in vitro dissolution studies, especially for more insoluble uranium compounds. A long-term follow-up of urinary excretion after the cessation of chronic inhalation exposure can provide a better estimate of the slow-rate dissolution. In this study, two workers, previously working for >20 y at a nuclear fuel fabrication plant, provided urine samples regularly for up to 6 y. One individual had worked at the pelletizing workshop with the known presence of uranium dioxide (UO 2 ) and triuranium octoxide (U 3 O 8 ). The second individual worked at the conversion workshop where multiple compounds, including uranium hexafluoride (UF 6 ), uranium dioxide (UO 2 ), ammonium uranyl carbonate, and AUC [UO 2 CO 3 ·2(NH 4 ) 2 CO 3 ], are present. Data on uranium concentration in urine during working years were also available for both workers. The daily excretion of uranium by urine was characterized by applying non-linear least square regression fitting to the urinary data. Material-specific parameters, such as the activity median aerodynamic diameter (AMAD), the respiratory tract absorption parameters, rapid fraction ( f r ,), rapid dissolution rate ( s r , d -1 ), and slow dissolution rate ( s s , d -1 ) and alimentary tract transfer factor ( f A ) acquired from previous work along with default absorption types, were applied to urine data, and the goodness of fit was evaluated. Thereafter intake estimates and dose calculations were performed. For the ex-pelletizing worker, a one-compartment model with a clearance half-time of 662 ± 100 d ( s s = 0.0010 d -1 ) best represented the urinary data. For the ex-conversion worker, a two-compartment model with a major [93% of the initial urinary excretion (A 0 )] fast compartment with a clearance half-time of 1.3 ± 0.4 d ( s r = 0.5 d -1 ) and a minor (7% of A 0 ) slow compartment with a half-time of 394 ± 241 d ( s s = 0.002 d -1 ) provided the best fit. The results from the data-fitting of urinary data to biokinetic models for the ex-conversion worker demonstrated that in vitro derived experimental parameters (AMAD = 20 µm, f r = 0.32, s r = 27 d -1 , s s = 0.0008 d -1 , f A = 0.005) from our previous work best represented the urinary data. This resulted in an estimated intake rate of 0.66 Bq d -1 . The results from the data-fitting of urinary data to biokinetic models for the ex-pelletizing worker indicated that the experimental parameters (AMAD = 10 µm and 20 µm, f r = 0.008, s r = 12 d -1 , f A = 0.00019) from our previous dissolution studies with the slow rate parameter step-wise optimized to urine-data ( s s = 0.0008 d -1 ) gave the best fit. This resulted in an estimated intake rate of 5 Bq d -1 . Experimental parameters derived from in vitro dissolution studies provided the best fit for the subject retired from work at the conversion workshop, where inhalation exposure to a mix of soluble (e.g., AUC, UF 6 ) and relatively insoluble aerosol (e.g., UO 2 ) can be assumed. For the subject retired from work at the pelletizing workshop, which involved exposure to relatively insoluble aerosols (UO 2 and U 3 O 8 ), a considerably higher s s than obtained in dissolution studies provided a better representation of the urinary data and was comparable to reported s s values for UO 2 and U 3 O 8 in other studies. This implies that in vitro dissolution studies of insoluble material can be uncertain. When evaluating the results from the retrospective fitting of urine data, it is evident that the urine samples acquired after cessation of exposure provide less fluctuation. Long-term follow-up of uranium excretion after cessation of exposure is a good alternative for determining absorption parameters and can be considered the most viable way for determining the slow rate for more insoluble material.

Hopping conduction in Mn ion-implanted GaAs nanowires.

We report on temperature-dependent charge transport in heavily doped Mn(+)-implanted GaAs nanowires. The results clearly demonstrate that the transport is governed by temperature-dependent hopping processes, with a crossover between nearest neighbor hopping and Mott variable range hopping at about 180 K. From detailed analysis, we have extracted characteristic hopping energies and corresponding hopping lengths. At low temperatures, a strongly nonlinear conductivity is observed which reflects a modified hopping process driven by the high electric field at large bias.

Particle Size Dependent Dissolution of Uranium Aerosols in Simulated Gastrointestinal Fluids.

ABSTRACT: Uranium aerosol exposure can be a health risk factor for workers in the nuclear fuel industry. Good knowledge about aerosol dissolution and absorption characteristics in the gastrointestinal tract is imperative for solid dose assessments and risk management. In this study, an in vitro dissolution model of the GI tract was used to experimentally study solubility of size-fractionated aerosols. The aerosols were collected from four major workshops in a nuclear fuel fabrication plant where uranium compounds such as uranium hexafluoride (UF 6 ), uranium dioxide (UO 2 ), ammonium uranyl carbonate, AUC [UO 2 CO 3 ·2(NH 4 ) 2 CO 3 ] and triuranium octoxide (U 3 O 8 ) are present. The alimentary tract transfer factor, f A , was estimated for the aerosols sampled in the study. The transfer factor was derived from the dissolution in the small intestine in combination with data on absorption of soluble uranium. Results from the conversion workshop indicated a f A in line with what is recommended (0.004) by the ICRP for inhalation exposure to Type M materials. Obtained transfer factors, f A , for the powder preparation and pelletizing workshops where UO 2 and U 3 O 8 are handled are lower for inhalation and much lower for ingestion than those recommended by the ICRP for Type M/S materials f A = 0.00029 and 0.00016 vs. 0.0006 and 0.002, respectively. The results for ingestion and inhalation f A indicate that ICRP's conservative recommendation of f A for inhalation exposure is applicable to both ingestion and inhalation of insoluble material in this study. The dissolution- and subsequent absorption-dependence on particle size showed correlation only for one of the workshops (pelletizing). The absence of correlation at the other workshops may be an effect of multiple chemical compounds with different size distribution and/or the reported presence of agglomerated particles at higher cut points having more impact on the dissolution than particle size. The impact on dose coefficients [committed effective dose (CED) per Bq] of using experimental f A vs. using default f A recommended by the ICRP for the uranium compounds of interest for inhalation exposure was not significant for any of the workshops. However, a significant impact on CED for ingestion exposure was observed for all workshops when comparing with CED estimated for insoluble material using ICRP default f A . This indicates that the use of experimentally derived site-specific f A can improve dose assessments. It is essential to acquire site-specific estimates of the dissolution and absorption of uranium aerosols as this provides more realistic and accurate dose- and risk-estimates of worker exposure. In this study, the results indicate that ICRP's recommendations for ingestion of insoluble material might overestimate absorption and that the lower f A found for inhalation could be more realistic for both inhalation and ingestion of insoluble material.